Semiconductor device including barrier layer between active region and semiconductor layer and method of forming the same

Abstract

A semiconductor device includes; an active region; an isolation region defining the active region; a barrier layer on the active region; an upper semiconductor layer on the barrier layer; and a gate structure covering an upper surface, a lower surface, and side surfaces of the upper semiconductor layer in a first direction. The first direction is a direction parallel to an upper surface of the active region, and the barrier layer is disposed between the gate structure and the active region.

Claims

1. A semiconductor device, comprising: a substrate; an active region on the substrate; an isolation region on the substrate and on side surfaces of the active region; a first source/drain region and a second source/drain region on the active region and spaced apart from each other; a barrier layer on and physically contacting the active region; a lower semiconductor layer on and physically contacting the barrier layer; upper semiconductor layers on the lower semiconductor layer and spaced apart from each other in a vertical direction; and a gate structure covering an upper surface, a lower surface, and side surfaces of each of the upper semiconductor layers in a first direction and extending on the isolation region, wherein the vertical direction is perpendicular to an upper surface of the substrate, wherein the first direction is parallel to the upper surface of the substrate, wherein a material of the barrier layer is different from a material of the upper semiconductor layers and a material of the lower semiconductor layer, and wherein the upper semiconductor layers, the lower semiconductor layer, and at least a portion of the barrier layer are between the first source/drain region and the second source/drain region.

2. The semiconductor device of claim 1, wherein lower surfaces of the first source/drain region and the second source/drain region physically contact the active region.

3. The semiconductor device of claim 1, wherein lower surfaces of the first source/drain region and the second source/drain region are at a lower level than a lower surface of the barrier layer.

4. The semiconductor device of claim 1, wherein a lower surface of the barrier layer is at a lower level than a lower surface of the gate structure adjacent to a side surface of the barrier layer.

5. The semiconductor device of claim 1, wherein a lower surface of the barrier layer is at a higher level than a lower surface of the gate structure adjacent to a side surface of the barrier layer.

6. The semiconductor device of claim 1, wherein the barrier layer includes a barrier impurity element, and wherein the upper semiconductor layers and the lower semiconductor layer do not include the barrier impurity element.

7. The semiconductor device of claim 1, wherein a thickness of the lower semiconductor layer is different from a thickness of at least one of the upper semiconductor layers.

8. The semiconductor device of claim 1, wherein the lower semiconductor layer physically contacts an upper surface of the barrier layer.

9. The semiconductor device of claim 1, wherein the lower semiconductor layer and the upper semiconductor layers are configured as channels.

10. The semiconductor device of claim 1, wherein the lower semiconductor layer and the barrier layer have a same width in a second direction perpendicular to the vertical direction and the first direction.

11. The semiconductor device of claim 1, wherein the barrier layer is doped with oxygen.

12. The semiconductor device of claim 11, wherein a concentration of oxygen in the barrier layer is in a range from 10.sup.15 atoms/cm.sup.3 to 10.sup.22 atoms/cm.sup.3.

13. The semiconductor device of claim 1, wherein the barrier layer is doped with an impurity element, and wherein a concentration of the impurity element in a lower region of the barrier layer is higher than a concentration of the impurity element in an upper region of the barrier layer.

14. A semiconductor device, comprising: an active region; an isolation region on side surfaces of the active region; a first source/drain region and a second source/drain region on the active region and spaced apart from each other; a barrier layer on and physically contacting the active region; a lower semiconductor layer on and physically contacting the barrier layer; upper semiconductor layers on the lower semiconductor layer and spaced apart from each other in a vertical direction; and a gate structure covering an upper surface, a lower surface, and side surfaces of each of the upper semiconductor layers in a first direction and extending on the isolation region, wherein the vertical direction is perpendicular to the first direction, wherein a material of the barrier layer is different from a material of the upper semiconductor layers and a material of the lower semiconductor layer, and wherein the upper semiconductor layers, the lower semiconductor layer, and at least a portion of the barrier layer are between the first source/drain region and the second source/drain region.

15. The semiconductor device of claim 14, wherein lower surfaces of the first source/drain region and the second source/drain region physically contact the active region.

16. The semiconductor device of claim 14, wherein lower surfaces of the first source/drain region and the second source/drain region are at a lower level than a lower surface of the barrier layer.

17. The semiconductor device of claim 14, wherein a thickness of the lower semiconductor layer is different from a thickness of at least one of the upper semiconductor layers.

18. A semiconductor device, comprising: a first source/drain region and a second source/drain region spaced apart from each other; an active region including a portion between the first source/drain region and the second source/drain region; a barrier layer on and physically contacting the active region; a lower semiconductor layer on and physically contacting the barrier layer; upper semiconductor layers on the lower semiconductor layer and spaced apart from each other in a vertical direction; and a gate structure covering an upper surface, a lower surface, and side surfaces of each of the upper semiconductor layers in a first direction, wherein the vertical direction is perpendicular to the first direction, wherein a material of the barrier layer is different from a material of the upper semiconductor layers and a material of the lower semiconductor layer, and wherein the upper semiconductor layers, the lower semiconductor layer, the barrier layer, and the portion of the active region are between the first source/drain region and the second source/drain region.

19. The semiconductor device of claim 18, wherein a thickness of the lower semiconductor layer is different from a thickness of at least one of the upper semiconductor layers.

20. The semiconductor device of claim 18, wherein the active region is in physical contact with the first source/drain region and the second source/drain region.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The above and other aspects, features and other advantages of the inventive concept will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 is a plan view illustrating a semiconductor device according to example embodiments;

(3) FIG. 2 is a cross-sectional view illustrating a semiconductor device according to an example embodiment;

(4) FIG. 3A is a partially enlarged cross-sectional view illustrating an example of a semiconductor device according to an example embodiment;

(5) FIG. 3B is a partially enlarged cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(6) FIG. 4 is a graph illustrating an impurity concentration in a portion of layers of a semiconductor device according to an example embodiment;

(7) FIG. 5A is a partially enlarged cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(8) FIG. 5B is a partially enlarged cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(9) FIG. 6A is a partially enlarged cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(10) FIG. 6B is a partially enlarged cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(11) FIG. 7 is a cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(12) FIG. 8 is a cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(13) FIG. 9 is a cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(14) FIG. 10 is a cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(15) FIG. 11A is a cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(16) FIG. 11B is a cross-sectional view illustrating a modified example of a semiconductor device according to an example embodiment;

(17) FIG. 12 is a process flow diagram illustrating a method of forming a semiconductor device according to an example embodiment; and

(18) FIGS. 13 to 19 are respective cross-sectional views illustrating an example of a method of forming a semiconductor device according to an example embodiment.

DETAILED DESCRIPTION

(19) A semiconductor device 1 according to embodiments of the inventive concept will now be described with reference to FIGS. 1, 2, and 3A, wherein FIG. 1 is a plan view of the semiconductor device 1, FIG. 2 includes cross-sectional views of the semiconductor device 1 taken along line I-I and line II-II of FIG. 1, and FIG. 3A is an enlarged, partial view of a portion A of FIG. 2.

(20) Referring collectively to FIGS. 1, 2, and 3A, the semiconductor device 1 comprises an active region 50b, a barrier layer 16 on the active region 50b, a plurality of semiconductor layers 30c and 33 on the barrier layer 16, a gate structure 83, and source/drain regions 71. The semiconductor device 1 may further comprise a substrate 5 and an isolation region 52.

(21) The substrate 5 may be a semiconductor substrate such as a silicon substrate, wherein the isolation region 52 may be disposed in a field trench 50a of the substrate 5 to define the active region 50b. The isolation region 52 may be formed of an insulating material such as silicon oxide.

(22) The active region 50b may include a well region 10 including a well impurity element. The well region 10 may be an N-type or a P-type well. For example, the well region 10 may include one or more N-type well impurity element(s) such as phosphorus (P) or arsenic (As), or the well region may include one or more P-type well impurity element(s) such as boron (B).

(23) As one example, the well region 10 shown in FIG. 2 is disposed in the active region 50b and extends to the substrate 5 below the isolation region 52.

(24) The barrier layer 16 may be disposed between the plurality of semiconductor layers 30c and 33 and the active region 50b. The barrier layer 16 may include a barrier impurity element. Here, the provision of the barrier layer 16 prevents (or significantly reduces) the diffusion of well impurity element(s) from the well region 10 to the plurality of semiconductor layers 30c and 33.

(25) In one example, the barrier layer 16 may include an epitaxial, crystalline material layer grown from the active region 50b. Thus, in certain embodiments of the inventive concept the barrier layer 16 may be referred to as a barrier epitaxial material layer.

(26) In one example, the active region 50b may be a crystalline silicon material layer, and the barrier layer 16 may include an epitaxial silicon material layer doped with one or more barrier impurity element(s) using an in-situ process while being epitaxially grown in a crystalline layer from an upper surface 50U of the active region 50b. The barrier impurity element(s) of the barrier layer 16 may be different from the well impurity element(s) of the well region 10. For example, oxygen (O) may be used as a barrier impurity element for the barrier layer 16 (e.g., the barrier layer 16 may be an epitaxial silicon material layer doped with oxygen). Alternately or additionally, carbon (C) may be used as a barrier impurity element for the barrier layer 16.

(27) The barrier impurity element(s) of the barrier layer 16 may be included in concentration(s) capable of significantly reducing or preventing diffusion of the well impurity element(s) of the well region 10 into the plurality of semiconductor layers 30c and 33. while yet maintaining the barrier layer 16 in a crystalline form. For example, when the barrier layer 16 is an epitaxial silicon material layer doped with oxygen, wherein the concentration of oxygen in the barrier layer 16 ranges (e.g.,) from about 1E15 atoms/cm.sup.3 to about 1E22 atoms/cm.sup.3.

(28) The plurality of semiconductor layers 30c and 33 may be stacked and spaced apart from each other in a vertical direction Z perpendicular to the horizontal principal extension direction of an upper surface 50U of the active region 50b. Here, the terms vertical and horizontal are merely relative, spatial descriptors arbitrarily assigned for purposes of this description.

(29) In one example, the plurality of semiconductor layers 30c and 33 may include a lower semiconductor layer 30c and one or a plurality of upper semiconductor layers 33 disposed on the lower semiconductor layer 30c and spaced apart from the lower semiconductor layer 30c. For example, one or a plurality of upper semiconductor layers 33 may be disposed on the lower semiconductor layer 30c.

(30) In this regard, the one or the plurality of upper semiconductor layers 33 may be a plurality of upper semiconductor layers 34c, 38c, and 42c.

(31) The lower semiconductor layer 30c may be an epitaxial semiconductor layer grown from an upper surface of the barrier layer 16. For example, the lower semiconductor layer 30c may be an epitaxial silicon layer grown from an upper surface of the barrier layer 16. The lower semiconductor layer 30c may be in contact with the barrier layer 16. Here, the lower semiconductor layer 30c may be referred to as a lower epitaxial semiconductor layer or a lower epitaxial silicon layer.

(32) The plurality of upper semiconductor layers 34c, 38c, and 42c may be stacked and spaced apart from each other in the vertical direction Z.

(33) In certain embodiments of the inventive concept, each of the plurality of upper semiconductor layers 34c, 38c, and 42c may be an epitaxial semiconductor layer. For example, each of the plurality of upper semiconductor layers 34c, 38c, and 42c may be an epitaxial silicon layer. Here, each of the plurality of upper semiconductor layers 34c, 38c, and 42c may be referred to as an upper epitaxial semiconductor layer or an upper epitaxial silicon layer.

(34) In one example, at least a portion of the plurality of semiconductor layers 30c and 33 may be an un-doped epitaxial silicon material layer.

(35) In another example, at least a portion of the plurality of semiconductor layers 30c and 33 may include the same impurity element as those impurity element(s) used in the well impurity element in the well region 10. For example, at least a portion of the plurality of semiconductor layers 30c and 33, for example, the lower semiconductor layer 30c, may include the same impurity element as the well impurity element in the well region 10, and a concentration of the impurity element in the lower semiconductor layer 30c may be less than a concentration of the well impurity element in the well region 10.

(36) The source/drain regions 71 may be disposed on the active region 50b, extend in the vertical direction Z, and contact side surfaces 33S2 of the plurality of upper semiconductor layers 34c, 38c, and 42c in a second direction X. For example, the source/drain regions 71 may include a first source/drain region 71_1 and a second source/drain region 71_2, spaced apart from each other, and the plurality of upper semiconductor layers 34c, 38c, and 42c may be disposed between the first source/drain region 71_1 and the second source/drain region 71_2. The barrier layer 16 may further include a first portion between the first source/drain region 71_1 and the active region 50b, and a second portion between the second source/drain region 71_2 and the active region 50b.

(37) In one example, the gate structure 83 may extend to the isolation region 52 while overlapping the active region 50b. The gate structure 83 may extend in a first direction Y, and the active region 50b may extend in the second direction X, perpendicular to the first direction Y. Each of the first direction Y and the second direction X may be disposed parallel to the upper surface 50U of the active region 50b. The gate structure 83 may be disposed on the plurality of upper semiconductor layers 34c, 38c, 42c while filling a space between the plurality of upper semiconductor layers 34c, 38c, and 42c.

(38) The gate structure 83 may cover an upper surface, a lower surface, and side surfaces 33S1 in the first direction Y, of each of the plurality of upper semiconductor layers 34c, 38c, and 42c. The gate structure 83 may cover at least a portion of the side surfaces 30S1 of the lower semiconductor layer 30c in the first direction Y while covering an upper surface of the lower semiconductor layer 30c.

(39) The gate structure 83 may include a gate dielectric 85 and a gate electrode 87. The gate dielectric 85 may include silicon oxide and/or a high-k dielectric. The gate electrode 87 may include a conductive material. The gate dielectric 85 may be interposed between the gate electrode 87 and the plurality of semiconductor layers 30c and 33, between the gate electrode 87 and the source/drain regions 71, between the isolation region 52 and the gate electrode 87, and disposed on side surfaces of the gate electrode 87 positioned at a higher level than that of the plurality of semiconductor layers 30c and 33. In this context, the term higher level is a relative spatial descriptor used in relation to separation distances between various elements and the principal surface of the substrate 5.

(40) The semiconductor device 1 may further comprise a gate capping pattern 90 on the gate structure 83, contact plugs 93 on the source/drain regions 71, and gate spacers 65. The contact plugs 93 may include a first contact plug 93_1 electrically connected to the first source/drain region 71_1 and a second contact plug 93_2 electrically connected to the second source/drain region 71_2. The gate capping pattern 90 may be formed of an insulating material. The gate spacers 65 may be interposed between the gate capping pattern 90 and the contact plugs 93, and between the gate structure 83 and the contact plugs 93.

(41) In certain embodiments of the inventive concept, the barrier layer 16 may improve leakage current characteristics of the semiconductor device 1. For example, the source/drain regions 71, the plurality of semiconductor layers 30c and 33 used as a channel region between the source/drain regions 71, and the gate structure 83 may form a MOSFET having a three-dimensional channel structure. In such a MOSFET, the barrier layer 16 may block or significantly reduce a leakage current between the lower semiconductor layer 30c, of the plurality of semiconductor layers 30c and 33, and the substrate 5. Moreover, the barrier layer 16 may block or significantly reduce a leakage current between the source/drain regions 71 and the substrate 5. Thus, the barrier layer 16 may improve a function of the overall operating characteristics of the semiconductor device 1.

(42) In one example, the barrier impurity element in the barrier layer 16 may be uniformly distributed in the barrier layer 16. In another example, the concentration of the barrier impurity element in the barrier layer 16 may be higher at a lower region of the barrier layer 16 than in an upper region of the barrier layer 16. In still another example, the concentration of the barrier impurity element in the barrier layer 16 may gradually vary from a lower region in the barrier layer 16 to an upper region of the barrier layer 16.

(43) In certain embodiments of the inventive concept, the barrier layer 16 may include one or more first regions and one or more second regions. Here, a first region may be a region having a concentration of the barrier impurity element relatively higher than the second region(s). Alternatively, a first region may be a region including the barrier impurity element, whereas a second region may be a region lacking the barrier impurity element.

(44) In the illustrated example of FIG. 3B, the barrier layer 16 includes a plurality of first regions and a plurality of second regions. Here, analogous to FIG. 3A, FIG. 3B is an enlarged, partial view of region A in FIG. 2.

(45) Referring to FIG. 3B, the barrier layer 16a includes at least one first region 17 in contact with at least one second region 18.

(46) However, the first region 17 may be provided as a plurality of first regions, and the second region 18 may be provided as a plurality of second regions. In one example, the barrier layer 16a may include first regions 17a and 17b as well as a second region 18a, between the first regions 17a and 17b, spaced apart from each other in the vertical direction Z. As another example, the barrier layer 16a may include a plurality of first regions 17a, 17b, and 17c as well as a plurality of second regions 18a and 18b. The plurality of first regions 17a, 17b, and 17c as well as the plurality of second regions 18a and 18b may be stacked alternately in the vertical direction Z. Among the plurality of first regions 17a, 17b, and 17c as well as the plurality of second regions 18a and 18b, stacked alternately, a lowermost first region 17a may be disposed in a lowermost portion, and an uppermost first region 17c may be disposed in an uppermost portion.

(47) The plurality of second regions 18a and 18b may be different from the plurality of first regions 17a, 17b, and 17c. For example, the plurality of first regions 17a, 17b, and 17c may be a region including a barrier impurity element, and a concentration of a barrier impurity element of at least one among the plurality of second regions 18a and 18b may be about zero, or may be less than a concentration of a barrier impurity element in the plurality of first regions 17a, 17b, and 17c. For example, a concentration of a barrier impurity element of each of the plurality of second regions 18a and 18b may be about zero, or may be less than a concentration of a barrier impurity element in the plurality of first regions 17a, 17b, and 17c.

(48) Each of the plurality of first regions 17a, 17b, and 17c may be formed of a doped epitaxial semiconductor material including a barrier impurity element, for example, an epitaxial silicon material, and each of the plurality of second regions 18a and 18b may include an epitaxial semiconductor material not including a barrier impurity element, or including a smaller amount of a barrier impurity element as compared with the plurality of first regions 17a, 17b, and 17c, for example, an epitaxial silicon material. As an example, each of the plurality of second regions 18a and 18b may be formed of an un-doped epitaxial silicon material.

(49) Each of the plurality of first regions 17a, 17b, and 17c may be referred to as a first epitaxial region, and each of the plurality of second regions 18a and 18b may be referred to as a second epitaxial region.

(50) Each of the plurality of first regions 17a, 17b, and 17c may be referred to as a barrier region, and each of the plurality of second regions 18a and 18b may be referred to as a buffer region. For example, the plurality of first regions 17a, 17b, and 17c may be a barrier region suppressing diffusion or a leakage current. The plurality of second regions 18a and 18b may be a buffer region preventing amorphization of the plurality of first regions 17a, 17b, and 17c by increasing a concentration of a barrier impurity element in the plurality of first regions 17a, 17b, and 17c.

(51) FIG. 4 is a graph illustrating a concentration distribution of a well impurity element WIE and a barrier impurity element BIE in the barrier layer 16 and the well region 10. In a graph of FIG. 4, the axis labeled D indicates a depth in a direction from a surface of the lower semiconductor layer 30c to the well region 10, and the axis labeled C indicates an impurity concentration.

(52) Referring to FIG. 4, the barrier layer 16 may be disposed between the well region 10 and the lower semiconductor layer 30c. The barrier layer 16 may include a barrier impurity element BIE, and the well region 10 may include a well impurity element WIE. As an example, the barrier impurity element BIE may be oxygen (O), and the well impurity element WIE may be arsenic (As).

(53) The well impurity element WIE in the well region 10 is diffused, and a concentration of the well impurity element increases toward the barrier layer 16, so the concentration of the well impurity element reaches a maximum in the barrier layer 16. For example, the well impurity element WIE in the well region 10 is diffused, and thus may be filed-up at a boundary region between the barrier layer 16 and the well region 10 or in the barrier layer 16 adjacent to the well region 10. Thus, the barrier layer 16 may include the well impurity element WIE diffused from the well region 10 to be filed-up together with the barrier impurity element BIE. A concentration of the well impurity element WIE in the barrier layer 16 may be higher than a concentration of the well impurity element WIE in the well region 10. The barrier layer 16 may prevent or significantly reduce diffusion of the well impurity element WIE in the well region 10 into the lower semiconductor layer 30c.

(54) FIGS. 5A and 5B illustrate various modified examples for the thickness of the barrier layer 16. Thus, FIGS. 5A and 5B respectively illustrate the enlarged partial view of region A of FIG. 2.

(55) Referring to FIG. 5A, a barrier layer 16b may have a thickness 16H less than a thickness 33H of at least one among the plurality of semiconductor layers 30c and 33. For example, a thickness 16H of the barrier layer 16b may be less than a thickness 30H of the lower semiconductor layer 30c, and may be less than a thickness 33H of each of the plurality of upper semiconductor layers 33. The barrier layer 16 of FIGS. 2 and 3A may be replaced with the barrier layer 16b described above. As described above, a barrier layer 16b having a relatively less thickness 16H may improve a degree of integration of a semiconductor device.

(56) Referring to FIG. 5B, a barrier layer 16c may have a thickness 16Ha greater than a thickness 33H of at least one among the plurality of semiconductor layers 30c and 33. For example, a thickness 16Ha of the barrier layer 16b may be greater than a thickness 30H of the lower semiconductor layer 30c, and may be greater than a thickness 33H of each of the plurality of upper semiconductor layers 33. The barrier layer 16 of FIGS. 2 and 3A may be replaced with the barrier layer 16c described above. As described above, a barrier layer 16c having a relatively great thickness 16Ha may improve leakage current characteristics of a semiconductor device. Moreover, since the barrier layer 16c having a relatively great thickness 16Ha may act as a stressor applying stress to the source/drain regions (71 of FIG. 2) to improve carrier mobility in the plurality of semiconductor layers 30c and 33 used as a channel region formed between the source/drain regions (71 of FIG. 2), a function of a semiconductor device may be improved.

(57) In similar manner, FIGS. 6A and 6B illustrate various modified examples of the lower semiconductor layer 30c. Hence, FIGS. 6A and 6B are also enlarged partial views of region A of FIG. 2.

(58) Referring to FIG. 6A, a lower semiconductor layer 30c may have a thickness 30Ha less than a thickness 33Ha of each of the plurality of upper semiconductor layers 33. The lower semiconductor layer 30c, described above, may be replaced with the lower semiconductor layer (30c of FIGS. 2, 3A, 5A, and 5B), described previously.

(59) Referring to FIG. 6B, a lower semiconductor layer 30c may have a thickness 30Hb greater than a thickness 33Ha of each of the plurality of upper semiconductor layers 33. The lower semiconductor layer 30c, described above, may be replaced with the lower semiconductor layer (30c of FIGS. 2, 3A, 5A, and 5B), described previously.

(60) FIGS. 7 and 8 illustrate various modified examples of the barrier layer 16, the lower semiconductor layer 30c, and the source/drain regions 71, where FIG. 7 is a cross-sectional view of the region taken along line I-I of FIG. 1.

(61) Referring to FIG. 7, a barrier layer 16d and source/drain regions 71a directly contact each other (i.e., no intervening layers or elements are present). Here, the lower semiconductor layer 30d may have side surfaces 30S2 in the second direction X, and the source/drain regions 71a may be in contact with side surfaces 30S2 of the lower semiconductor layer 30d in the second direction X.

(62) The barrier layer 16d may include a first thickness portion and a second thickness portion, thinner than the first thickness portion. The first thickness portion of the barrier layer 16d may be a portion interposed between the lower semiconductor layer 30d and the active region 50b, and the second thickness portion of the barrier layer 16d may be a portion interposed between the source/drain regions 71a and the active region 50b.

(63) The barrier layer 16d, the lower semiconductor layer 30d, and the source/drain regions 71a, described above, may be replaced with the barrier layer (16 of FIG. 2), the lower semiconductor layer (30 of FIG. 2), and the source/drain regions (71 of FIG. 2), described previously.

(64) Referring to FIG. 8, the barrier layer 16e may be self-aligned with the lower semiconductor layer 30d having side surfaces in the second direction X as described with reference to FIG. 7. Thus, the barrier layer 16e may have side surfaces 16S2 in the second direction X. The source/drain regions 71b may be in direct contact with the well region 10 in the active region 50b. The source/drain regions 71b may be in contact with side surfaces of the lower semiconductor layer 30d in the second direction X and side surfaces 16S2 of the barrier layer 16e in the second direction X.

(65) The barrier layer 16e, the lower semiconductor layer 30d, and the source/drain regions 71b described above, may respectively replaced the barrier layer 16 of FIG. 2, the lower semiconductor layer 30 of FIG. 2, and/or the source/drain regions 71 of FIG. 2.

(66) FIGS. 9 and 10 illustrate various modified examples of the gate structure 83 and are respective cross-sectional views of the region taken along line II-II of FIG. 1.

(67) Referring to FIG. 9, a gate structure 83a covers side surfaces 16S1 of the lower semiconductor layer 30c in the first direction Y while covering an upper surface of the lower semiconductor layer 30c, and extends downward to cover at least a portion of side surfaces 16S1 of the barrier layer 16 in the first direction Y. The gate structure 83a may include a gate dielectric 85a and a gate electrode 87a, and the gate dielectric 85a may be in direct contact with at least a portion of an upper surface of the lower semiconductor layer 30c, side surfaces 16S1 of the lower semiconductor layer 30c in the first direction Y, and side surfaces 16S1 of the barrier layer 16 in the first direction Y. The gate structure 83a described above may replace the gate structure 83 of FIG. 2.

(68) Referring to FIG. 10, the gate structure 83b may cover portions of side surfaces 16S1 of the lower semiconductor layer 30c in the first direction Y, side surfaces 16S1 of the barrier layer 16 in the first direction Y, and side surfaces 50S of the active region 50b in the first direction Y, while covering an upper surface of the lower semiconductor layer 30c. The gate structure 83b may include a gate dielectric 85b and a gate electrode 87b, and the gate dielectric 85b may be in contact with portions of an upper surface of the lower semiconductor layer 30c, side surfaces 16S1 of the lower semiconductor layer 30c in the first direction Y, side surfaces 16S1 of the barrier layer 16 in the first direction Y, and side surfaces 50S of the active region 50b in the first direction Y. The gate structure 83b described above may replace the gate structure 83 of FIG. 2.

(69) FIG. 11A illustrates a modified example of the barrier layer 16 and the plurality of semiconductor layers 30c and 33 and is a cross-sectional view of the region taken along lines I-I and II-II of FIG. 1.

(70) Referring to FIG. 11A, among the plurality of semiconductor layers (30c and 33 of FIG. 2), the lower semiconductor layer 30c may be omitted. Thus, the plurality of upper semiconductor layers 33 may be disposed on the barrier layer 116.

(71) The gate structure 83 may include a gapfill portion 83g filling a space between a lowermost upper semiconductor layer 34c, of the plurality of upper semiconductor layers 33, and the barrier layer 116, while filling a space between the plurality of upper semiconductor layers 33. An upper surface of the barrier layer 116 may be in contact with the gapfill portion 83g of the gate structure 83.

(72) A portion of the side surfaces 116S1 of the barrier layer 116 in the first direction Y may be in contact with the gate structure 83. The barrier layer 116 may be in contact with the source/drain regions 71. The barrier layer 116 may include a first thickness portion, interposed between the gate structure 83 and the active region 50b, and a second thickness portion interposed between the source/drain regions 71 and the active region 50b. The first thickness portion of the barrier layer 116 may be thicker than the second thickness portion of the barrier layer 116.

(73) Referring back to FIG. 2, among the plurality of semiconductor layers 30c and 33, the lower semiconductor layer 30c may be omitted, and the barrier layer 116 may be replaced with the modified barrier layer 116 of FIG. 11A.

(74) FIG. 11B illustrates a modified example of the semiconductor device illustrated in FIG. 2 according to certain embodiments of the inventive concept. Hence, FIG. 11B is a cross-sectional view illustrating a region taken along line I-I of FIG. 1.

(75) Referring to FIG. 11B, the gapfill portion 83g of the gate structure 83 may be spaced apart from the source/drain regions 71. For example, the inner spacers 69 having insulating properties may be disposed between the gapfill portion 83g of the gate structure 83 and the source/drain regions 71.

(76) Referring now to FIGS. 1, 2 and 12 to 19 (inclusive), certain embodiments of the inventive concept directed to methods of fabricating a semiconductor device will be described. Here, FIG. 12 is a general process flow chart for the exemplary methods, and FIGS. 13 to 19 are respective, cross-sectional views illustrating a region taken along line I-I and a region taken along line II-II of FIG. 1.

(77) Referring to FIGS. 1, 12, and 13, a substrate 5 may be prepared. The substrate 5 may be a bulk semiconductor substrate or a Silicon On Insulator (SOI) substrate.

(78) A well formation process is performed, to form a well region 10 in the substrate 5 (S10). The well region 10 may be a P-type well region or an N-type well region. The well formation process may include injecting a well impurity element into the substrate 5 by performing an ion implantation process, and activation of the well impurity element in the substrate 5 by performing an annealing process.

(79) By performing a first epitaxial growth process, a first layer 15 including a barrier impurity element may be formed (S20). The first layer 15 may be a first epitaxial material layer, grown from the well region 10 of the substrate 5, and may be in-situ doped with the barrier impurity element.

(80) As an example, forming the first layer 15 for formation of the barrier layer (16a of FIG. 3B) described above with reference to FIG. 3B may include repeatedly performing a set of operations, wherein the set of operations includes: forming a doped epitaxial silicon layer (17a of FIG. 3B) grown from the well region 10, and doped with a barrier impurity element; forming an un-doped epitaxial silicon layer (18a of FIG. 3B) grown from the doped epitaxial silicon layer (17a of FIG. 3B), and forming a doped epitaxial silicon layer (17b of FIG. 3B) grown from the un-doped epitaxial silicon layer (18a of FIG. 3B) and doped with the barrier impurity element. As an example, the barrier impurity element may be oxygen (O) or carbon (C).

(81) Referring to FIGS. 1, 12, and 14, a second epitaxial growth process and a third epitaxial growth process are repeatedly performed to form a stacked structure 25a including second layers 30a, 34a, 38a, and 42a as well as third layers 32a, 36a, and 40a (S20). For example, forming the stacked structure 25a may include repeatedly performing a set of operations, wherein the set of operations includes a second epitaxial growth process and a third epitaxial growth process. For example, the second epitaxial growth process is performed to form a lowermost second layer 30a grown from the first layer 15, the third epitaxial growth process is performed to form a lowermost third layer 32a grown from the lowermost second layer 30a, the second epitaxial growth process is performed to form the other second layer 34a grown from the lowermost third layer 32a, and the third epitaxial growth process is performed to form the other third layer 36a grown from the other second layer 34a.

(82) In one example, the second layers 30a, 34a, 38a, and 42a may be an un-doped epitaxial silicon layer, and the third layers 32a, 36a, and 40a may be an epitaxial silicon germanium layer having etch selectivity with respect to the second layers 30a, 34a, 38a, and 42a.

(83) In one example, among the second epitaxial growth process and the third epitaxial growth process repeatedly performed, a second epitaxial growth process may be ultimately performed. For example, among the second layers 30a, 34a, 38a, and 42a, and the third layers 32a, 36a, and 40a, a layer positioned at a lowermost portion may be a lowermost second layer 30a, and a layer positioned at an uppermost portion may be an uppermost second layer 42a.

(84) As another example, among the second epitaxial growth process and the third epitaxial growth process repeatedly performed, a third epitaxial growth process may be ultimately performed.

(85) Referring to FIGS. 1 and 15, the stacked structure (25a of FIG. 14), the first layer 15 of FIG. 14) and the substrate 5 are etched to form a field trench 50a.

(86) The field trench 50a may define an active region 50b in the substrate 5. While the field trench 50a is formed, the first layer (15 of FIG. 14) is etched to be formed as a first pattern 16, and the stacked structure (25a of FIG. 14) is etched to be formed as a stacked line 25b.

(87) The first pattern 16 may be referred to as a barrier layer described previously with reference to FIG. 2. In the following method description, a reference numeral 16 refers to a first pattern.

(88) The stacked line 25b may include second lines 30b, 34b, 38b, and 42b formed by etching the second layers (30a, 34a, 38a, and 42a of FIG. 14), and third lines (32b, 36b, and 40b of FIG. 14) formed by etching the third layers (32a, 36a, and 40a of FIG. 14).

(89) Here, the well region 10 may remain in the active region 50b, where the well region 10 may remain in the substrate 5 below the field trench 50a while remaining in the active region 50b.

(90) An isolation region 52 partially filling the field trench 50a may be provided. The isolation region 52 may be formed of an insulating material such as silicon oxide, or the like.

(91) An upper surface of the isolation region 52 may be formed at a level, lower than that of an upper surface of a lowermost second line 30b, of the second lines 30b, 34b, 38b, and 42b, and higher than an upper surface of the first pattern 16.

(92) In a modified example, an upper surface of the isolation region 52 may be formed at a level lower than that of an upper surface of the first pattern 16, and higher than a lower surface of the first pattern 16.

(93) In another modified example, an upper surface of the isolation region 52 may be formed at a level lower than that of a lower surface of the first pattern 16.

(94) In an example, the active region 50b, the first pattern 16, and the stacked line 25b may be sequentially stacked and may be vertically aligned. The active region 50b, the first pattern 16, and the stacked line 25b may extend in the second direction X. The second direction X may be a direction parallel to an upper surface of the substrate 5.

(95) Referring to FIGS. 1 and 16, a sacrificial gate pattern 55 extending in the first direction Y, may be provided. The sacrificial gate pattern 55 may extend to the isolation region 52 while covering an upper surface of the stacked line 25b and side surfaces of the stacked line 25b in the first direction Y.

(96) The sacrificial gate pattern 55 may include a lower sacrificial gate pattern 57 and an upper sacrificial gate pattern 59 on the lower sacrificial gate pattern 57.

(97) As an example, the lower sacrificial gate pattern 57 may be formed of polysilicon, and the upper sacrificial gate pattern 59 may be formed of silicon nitride.

(98) Gate spacers 65 may be formed on side surfaces of the sacrificial gate pattern 55. The gate spacers 65 may be formed of an insulating material.

(99) Referring to FIGS. 1 and 17, the stacked line (25b of FIG. 16) is etched using an etching process with the sacrificial gate pattern 55 and the gate spacers 65, used as an etching mask, to form recesses 68. While the recesses 68 are formed, the stacked line (25b of FIG. 16) is etched to be formed as a stacked pattern 25c.

(100) The second lines (30b, 34b, 38b, and 42b of FIG. 16) of the stacked line (25b of FIG. 16) are etched to be formed as second patterns (30c, 34c, 38c, and 42c), and the third lines (32b, 36b, and 40b of FIG. 16) of the stacked line (25b of FIG. 16) are etched to be formed as third patterns (32c, 36c, and 40c).

(101) As an example, a bottom surface of the recesses 68 may be located lower than a bottom surface of a lowermost third pattern 32c, of the third patterns 32c, 36c, and 40c, and may be located higher than a bottom surface of a lowermost second pattern 30c, of the second patterns 30c, 34c, 38c, and 42c.

(102) In a modified example, a bottom surface of the recesses 68 may be located higher than a bottom surface of the first pattern 16, and may be located lower than an upper surface of the first pattern 16.

(103) In another modified example, a bottom surface of the recesses 68 may be located lower than a bottom surface of the first pattern 16.

(104) As an example, a lowermost second pattern 30c, of the second patterns 30c, 34c, 38c, and 42c, may be referred to as a lower semiconductor layer described previously with reference to FIG. 2, and the remaining second patterns 34c, 38c, and 42c, formed on the lowermost second pattern 30c, may be referred to as upper semiconductor layers described previously with reference to FIG. 2.

(105) Referring to FIGS. 1 and 18, source/drain regions 71 may be formed in the recesses 68. The source/drain regions 71 may be a source/drain epitaxial material layer, grown from a surface of the stacked pattern 25c exposed by the recesses 68, by performing a source/drain epitaxial growth process.

(106) The source/drain regions 71 may include an N-type source/drain impurity element or a P-type source/drain impurity element.

(107) As an example, the source/drain regions 71 may a first source/drain region 71_1 and a second source/drain region 71_2, spaced apart from each other.

(108) Then, an insulating layer is formed on the substrate 5 having the source/drain regions 71, and the insulating layer is planarized until the lower sacrificial gate pattern 57 is exposed to form an interlayer insulating layer 74. The interlayer insulating layer 74 may be formed on the source/drain regions 71, and may have an upper surface coplanar with an upper surface of the lower sacrificial gate pattern 57.

(109) Referring to FIGS. 1 and 19, the lower sacrificial gate pattern (57 of FIG. 18) is selectively removed to form a gate trench 77. While the gate trench 77 is formed, side surfaces of the third patterns (32c, 36c, and 40c of FIG. 18) may be exposed.

(110) After the gate trench 77 is formed, the third patterns (32c, 36c, and 40c of FIG. 18), having side surfaces exposed by the gate trench 77, are removed to form interlayer spaces 80.

(111) As described previously, the first pattern 16 may be referred to as a barrier layer described previously with reference to FIG. 2. The first pattern 16, which may be such a barrier layer, may prevent or significantly reduce diffusion of a well impurity element in the well region 10 into the second patterns 30c, 34c, 38c, and 42c as well as the third patterns 32c, 36c, and 40c, using various processes. The various processes may include epitaxial growth processes for formation of the second patterns 30c, 34c, 38c, and 42c as well as the third patterns 32c, 36c, and 40c, an epitaxial growth process for formation of the source/drain regions 71, and an annealing process for activation of source/drain impurity elements allowing the source/drain regions 71 to have N-type or P-type conductivity. As described above, a well impurity element is not diffused into the third patterns 32c, 36c, and 40c, so the third patterns (32c, 36c, and 40c of FIG. 18) may be stably and completely removed.

(112) Again, referring to FIGS. 1 and 2, a gate structure 83, partially filling the gate trench (77 of FIG. 19) while filling the interlayer spaces (80 of FIG. 19), may be provided. The gate structure 83 may include a gate dielectric 85 and a gate electrode 87. The gate dielectric 85 may include silicon oxide and/or a high-k dielectric. The gate electrode 87 may include a conductive material.

(113) A gate capping pattern 90 filling a remaining portion of the gate trench (77 of FIG. 19) may be formed on the gate structure 83. The gate capping pattern 90 may be formed of an insulating material such as silicon oxide and/or silicon nitride.

(114) After the interlayer insulating layer (74 of FIG. 19), located on the source/drain regions 71, is etched, contact plugs 93 may be formed on the source/drain regions 71. The contact plugs 93 may include a first contact plug 93_1, formed on the first source/drain region 71_1, and a second contact plug 93_2, formed on the second source/drain region 71_2.

(115) As described above with reference to certain embodiments of the inventive concept, a semiconductor device may be provided in which a barrier layer is interposed between an active region and a semiconductor layer, wherein the barrier layer prevents or significantly reduces leakage current that may otherwise occur between the semiconductor layer which may be used as a channel, and an active region. The barrier layer may prevent or significantly reduce diffusion of a well impurity region of a well region in an active region into the semiconductor layer.

(116) While example embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the appended claims.