Abstract
Between a source electrode (25) of a main device (24) and a current sensing electrode (22) of a current detection device (21), a resistor for detecting current is connected. Dielectric withstand voltage of gate insulator (36) is larger than a product of the resistor and maximal current flowing through the current detection device (21) with reverse bias. A diffusion length of a p-body region (32) of the main device (24) is shorter than that of a p-body (31) of the current detection device (21). A curvature radius at an end portion of the p-body region (32) of the main device (24) is smaller than that of the p-body (31) of the current detection device (21). As a result, at the inverse bias, electric field at the end portion of the p-body region (32) of the main device (24) becomes stronger than that of the p-body region (31) of the current detection device (21). Consequently, avalanche breakdown tends to occur earlier in the main device 24 than the current detection device (21).
Claims
1. A semiconductor device that detects current in a main insulated-gate semiconductor device element by a potential difference, the semiconductor device, comprising: the main insulated-gate semiconductor device element; a current-detecting insulated-gate semiconductor device element having a size smaller than a size of the main insulated-gate semiconductor device element; and a resistor connected between the main insulated-gate semiconductor device element and the current-detecting insulated-gate semiconductor device element, the resistor having the potential difference between ends thereof, wherein the current-detecting insulated-gate semiconductor device element, under reverse bias, has a breakdown voltage higher than a breakdown voltage of the main insulated-gate semiconductor device element under reverse bias, the main insulated-gate semiconductor device element has: a first first-conductivity-type semiconductor layer having a first main surface and a second main surface opposite to each other, a first second-conductivity-type semiconductor region provided in the first first-conductivity-type semiconductor layer at the first main surface, a first first-conductivity-type high-concentration semiconductor region selectively provided in the first second-conductivity-type semiconductor region at a surface of the first second-conductivity-type semiconductor region, a first gate electrode provided, via a first gate insulating film, in a first trench that penetrates the first first-conductivity-type high-concentration semiconductor region and the first second-conductivity-type semiconductor region and reaches the first first-conductivity-type semiconductor layer, a first electrode in contact with the first first-conductivity-type high-concentration semiconductor region and the first second-conductivity-type semiconductor region, and a second electrode provided facing the second main surface of the first first-conductivity-type semiconductor layer, and the current-detecting insulated-gate semiconductor device element has: a second first-conductivity-type semiconductor layer having a first main surface and a second main surface opposite to each other, a second second-conductivity-type semiconductor region provided in the second first-conductivity-type semiconductor layer at the first main surface of the second first-conductivity-type semiconductor layer, a second first-conductivity-type high-concentration semiconductor region selectively provided in the second second-conductivity-type semiconductor region at a surface of the second second-conductivity-type semiconductor region, a second gate electrode provided, via a second gate insulating film, in a second trench that penetrates the second first-conductivity-type high-concentration semiconductor region and the second second-conductivity-type semiconductor region and reaches the second first-conductivity-type semiconductor layer, a third electrode in contact with the second first-conductivity-type high-concentration semiconductor region and the second second-conductivity-type semiconductor region, and a fourth electrode provided facing the second main surface of the second first-conductivity-type semiconductor layer.
2. The semiconductor device according to claim 1, wherein the resistor is connected between the first electrode and the third electrode, the second electrode and the fourth electrode are short-circuited, the first second-conductivity-type semiconductor region is divided into a plurality of regions by the first trench, one of the regions is floating electrically from the first electrode, a short-circuit ratio of the second second-conductivity-type semiconductor region with the third electrode is higher than a short-circuit ratio of the first second-conductivity-type semiconductor region with the first electrode.
3. The semiconductor device according to claim 1, wherein the resistor is connected between the first electrode and the third electrode, the second electrode and the fourth electrode are short-circuited, and the first trench has a width that is less than a width of the second trench.
4. The semiconductor device according to claim 1, wherein the resistor is connected between the first electrode and the third electrode, the second electrode and the fourth electrode are short-circuited, and a diffusion depth of the first second-conductivity-type semiconductor region is shallower than a diffusion depth of the second second-conductivity-type semiconductor region.
5. The semiconductor device according to claim 1, wherein the resistor is connected between the first electrode and the third electrode, the second electrode and the fourth electrode are short-circuited, and the first trench is deeper than the second trench.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) FIG. 1 is a sectional view of a semiconductor device with a current detection function according to a first embodiment;
(2) FIG. 2 is a sectional view of a semiconductor device with a current detection function according to a second embodiment;
(3) FIG. 3 is a section view of a semiconductor device with a current detection function according to a third embodiment;
(4) FIG. 4 is a sectional view of a semiconductor device with a current detection function according to a fourth embodiment;
(5) FIG. 5 is a sectional view of a semiconductor device with a current detection function according to a fifth embodiment;
(6) FIG. 6 is a sectional view of a semiconductor device with a current detection function according to a sixth embodiment;
(7) FIG. 7 is a sectional view of a semiconductor device with a current detection function according to a seventh embodiment;
(8) FIG. 8 is a sectional view of a semiconductor device with a current detection function according to an eighth embodiment;
(9) FIG. 9 is a sectional view of a semiconductor device with a current detection function according to a ninth embodiment;
(10) FIG. 10 is a plan view illustrating a configuration of a semiconductor device having a current detection function according to a tenth embodiment;
(11) FIG. 11 is a cross-sectional view of the semiconductor device having a current detection function according to the tenth embodiment;
(12) FIG. 12 is a cross-sectional view of a semiconductor device having a current detection function according to an eleventh embodiment;
(13) FIG. 13 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twelfth embodiment;
(14) FIG. 14 is a cross-sectional view of a semiconductor device having a current detection function according to a thirteenth embodiment;
(15) FIG. 15 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a fourteenth embodiment;
(16) FIG. 16 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a fifteenth embodiment;
(17) FIG. 17 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a sixteenth embodiment;
(18) FIG. 18 is a cross-sectional view illustrating a semiconductor device having a current detection function according to the seventeenth embodiment;
(19) FIG. 19 is a cross-sectional view illustrating a semiconductor device having a current detection function according to an eighteenth embodiment;
(20) FIG. 20 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a nineteenth embodiment;
(21) FIG. 21 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twentieth embodiment;
(22) FIG. 22 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-first embodiment;
(23) FIG. 23 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-second embodiment;
(24) FIG. 24 is a cross sectional view illustrating a semiconductor device having a current detection function according to a twenty-third embodiment;
(25) FIG. 25 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-fourth embodiment;
(26) FIG. 26 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-fifth embodiment;
(27) FIG. 27 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-sixth embodiment;
(28) FIG. 28 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-seventh embodiment;
(29) FIG. 29 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-eighth embodiment;
(30) FIG. 30 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-ninth embodiment;
(31) FIG. 31 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a thirtieth embodiment;
(32) FIG. 32 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a thirty-first embodiment;
(33) FIG. 33 is a cross-sectional view of a semiconductor device having a current detection function according to a thirty-second embodiment;
(34) FIG. 34 is a diagram illustrating relationships between a device structure of IGBT and the withstand voltage of the device;
(35) FIG. 35 is a plan view of a semiconductor device with a current detection function;
(36) FIG. 36 is a sectional view along a line A-A′ depicted in FIG. 35;
(37) FIG. 37 is a sectional view of a conventional semiconductor device with a current detection function;
(38) FIG. 38 is a sectional view of another example of a conventional semiconductor device with a current detection function; and
(39) FIG. 39 is a cross-sectional view illustrating a structure of the conventional semiconductor device having a dummy trench structure and a current detection function.
EXPLANATIONS OF LETTERS OR NUMERALS
(40) 10 resistor
(41) 21 current detection device
(42) 22 current sensing electrode
(43) 23, 26 gate electrode
(44) 24 main device
(45) 25 source electrode
(46) 27 n-drift layer
(47) 28 drain electrode
(48) 31, 32 p-body region
(49) 33, 34 trench
(50) 35, 38 n.sup.+ source region
(51) 36, 39 gate insulator
(52) 37, 40 interlayer isolator
(53) 41 n.sup.+ high density region
(54) 42 p-collector layer
(55) 81, 82 p-type floating layer
(56) 83, 84 trench gate electrodes
(57) 85, 86 dummy trench electrode
BEST MODE(S) FOR CARRYING OUT THE INVENTION
(58) Referring to the accompanying drawings, exemplary embodiments of a semiconductor device according to the present invention are explained in detail below. In the specification and the accompanying drawings, the names of layers and regions having an “n” or “p” prefix indicate that electrons or holes are a majority carrier. Any region with symbol “+” appended indicates that the region has a higher impurity density than layers or regions without “+”. In the explanation of embodiments and the drawings, identical components are given the same respective reference numerals, and redundant explanations are omitted.
First Embodiment
(59) FIG. 1 is a sectional view of a semiconductor device with a current detection function according to a first embodiment. As depicted in FIG. 1, a semiconductor device according to the first embodiment is a planar gate MOSFET. A current detection device 21 is formed on the same semiconductor substrate as a main device 24. An n-drift layer 27 and a drain electrode 28 are shared between the current detection device 21 and the main device 24. The current detection device 21 and the main device 24 are separated by, for example, a p-separation region (not shown). The size of the current detection device 21 is smaller than the size of the main device 24.
(60) A structure of the current detection device 21 is described. A p-body region 31 is selectively deposited in a surface layer of a first principal surface of an n-type semiconductor substrate (the n-drift layer 27). An n.sup.+ source region 35 is selectively deposited in a surface layer of the p-body region 31. A gate insulator film 36 contacts a surface of a region of the p-body region 31 between the n.sup.+ source region 35 and the n-drift layer 27. A gate electrode 23 is deposited on the gate insulator film 36. The gate electrode 23 is covered by an interlayer insulator 37. A current sensing electrode 22 contacts the n.sup.+ source region 35 and the p-body region 31 at a contact hole that opens through the interlayer insulator 37. The drain electrode 28 contacts a second principal surface.
(61) A structure of the main device 24 is described. A p-body region 32 is selectively deposited in a surface layer of a first principal surface of an n-type semiconductor substrate (n-drift layer 27). An n.sup.+ source region 38 is selectively deposited in a surface layer of the p-body region 32. A gate insulator film 39 contacts a surface of part of the p-body region 32 between the n.sup.+ source region 38 and the n-drift layer 27. A gate electrode 26 is deposited on the gate insulator film 39. The gate electrode 26 is covered by an interlayer insulator 40. A source electrode 25 contacts the n.sup.+ source region 38 and the p-body region 32 at a contact hole that opens through the interlayer insulator 40.
(62) A resistor for current detection is placed between and connected with the source electrode 25 and the current sensing electrode 22. The resistor for current detection may be formed on the same semiconductor substrate as the current detection device 21 and the main device 24, or may be an external resistor connected with a semiconductor chip having the current detection device 21 and the main device 24.
(63) For example, patterning of an insulator such as an oxide film covering the first principal surface of the substrate forms the gate insulator film 26 of the current detection device 21 and the gate insulator film 39 of the main device, simultaneously. As a result, the insulators 36 and 39 have substantially the same thickness. The thickness of the insulators 36 and 39 is designed in such a manner that withstand voltage of the gate insulator film 36 is larger than a product of resistance of the resistor for current detection and the maximum current through the current detection device 21 under reverse bias.
(64) Diffusion depth of the p-body region 32 of the main device 24 is designed to be shallower than diffusion depth of the p-body region 31 of the current detection device 21. In this case, curvature of an edge part of the p-body region 32 becomes smaller than curvature of an edge part of the p-body region 31. Consequently, under reverse bias, the electrical field around the edge part of the p-body region 32 becomes stronger than the electrical field around the edge part of the p-body region 31 so that avalanche breakdown tends to occur in the main device 24 before in the current detection device 21, thereby preventing the current detection device 21 from being damaged before the main device 24. In other words, the current detection device 21 has higher withstand voltage than the main device 24 under the reverse bias.
Second Embodiment
(65) FIG. 2 is a sectional view of a semiconductor device with a current detection function according to a second embodiment. As depicted in FIG. 2, an interval between adjacent p-body regions 32 of the main device 24 is greater than an interval between adjacent p-body regions 31 of the current detection device 21. Curvature of an edge part and diffusion depth of the p-body regions 31 and 32 are the same. Other details are similar to the first embodiment. Because of the widening of the interval between p-body regions 32 of the main device 24, avalanche breakdown tends to occur in the main device 24 before in the current detection device 21, thereby preventing the current detection device 21 from being damaged before the main device 24. Features of the first and second embodiments may be combined.
Third Embodiment
(66) FIG. 3 is a section view of a semiconductor device with a current detection function according to a third embodiment. As depicted in FIG. 3, a semiconductor device according to the third embodiment is a trench gate MOSFET. A trench 33 of the current detection device 21 extends through the n.sup.+ source region 35 and the p-body region 31 to the n-drift layer 27. The trench 33 is filled with the gate electrode 23 and the gate insulator film 36 enveloping the gate electrode 23. A trench 34 of the main device 24 extends through the n.sup.+ source region 38 and the p-body region 32 to the n-drift layer 27. The trench 34 is filled with the gate electrode 26 and the gate insulator film 39 enveloping the gate electrode 26. The trench 34 of the main device 24 is deeper than the trench 33 of the current detection device 21. Other details are similar to the first embodiment. Due to the deeper trench 34 of the main device 24, the withstand voltage of the current detection device 21 becomes higher than the withstand voltage of the main device 24 under reverse bias.
Fourth Embodiment
(67) FIG. 4 is a sectional view of a semiconductor device with a current detection function according to a fourth embodiment. As depicted in FIG. 4, an interval between adjacent trenches 34 of the main device 24 is greater than an interval between adjacent trenches 33 of the current detection device 21. Except for the depth of the trench 33 being substantially equal to depth of the trench 34, other details are similar to the third embodiment (this is also applicable to fifth to eighth embodiments). Due to the widening of the interval between the trenches 34 of the main device 24, withstand voltage becomes higher in the current detection device 21 than the main device 24 under reverse bias.
Fifth Embodiment
(68) FIG. 5 is a sectional view of a semiconductor device with a current detection function according to a fifth embodiment. As depicted in FIG. 5, the diffusion depth of the p-body region 32 of the main device 24 is shallower than the diffusion depth of the p-body region 31 of the current detection device 21. With this configuration as well, under reverse bias, the withstand voltage of the current detection device 21 becomes higher than the withstand voltage of the main device 24.
Sixth Embodiment
(69) FIG. 6 is a sectional view of a semiconductor device with a current detection function according to a sixth embodiment. As depicted in FIG. 6, in the main device 24, a boundary region between the n-drift layer 27 and the p-body region 32 is occupied by an n.sup.+ high density region 41. An n-type impurity density of the n.sup.+ high density region 41 is higher than an n-type impurity density of a boundary region between the n-drift layer 27 and the p-body region 31 of the current detection device 21. With this configuration as well, under reverse bias, withstand voltage of the current detection device 21 becomes higher than withstand voltage of the main device 24.
Seventh Embodiment
(70) FIG. 7 is a sectional view of a semiconductor device with a current detection function according to a seventh embodiment. As depicted in FIG. 7, the width of the trench 34 of the main device 24 is narrower than the width of the trench 33 of the current detection device 21. With this configuration as well, under reverse bias, the withstand voltage of the current detection device 21 becomes higher than withstand voltage of the main device 24.
Eighth Embodiment
(71) FIG. 8 is a sectional view of a semiconductor device with a current detection function according to an eighth embodiment. As depicted in FIG. 8, in the main device 24, the p-body region 32 is divided into multiple regions by the trenches 34, and some of the regions are covered by the interlayer insulators 40 and are electrically isolated from the source electrode 25. Also in the current detection device 21, though not shown, some of the p-body regions 31 are covered by the interlayer isolator films 37 and are isolated from the current sensing electrode 22. The electrically isolated regions of the p-body regions 31 and 32 do not include the n.sup.+ source regions 35 and 38. A ratio of making short circuit between the p-body region 31 and the current sensing electrode 22 is higher than a ratio of making short circuit between the p-body region 32 and the source electrode 25. With this configuration as well, under reverse bias, withstand voltage of the current detection device 21 becomes higher than withstand voltage of the main device 24. Two or more of the third to eighth embodiments may be combined.
Ninth Embodiment
(72) FIG. 9 is a sectional view of a semiconductor device with a current detection function according to a ninth embodiment. As depicted in FIG. 9, a semiconductor device of the ninth embodiment is a planar gate IGBT having a configuration similar to that of the semiconductor device according to the first embodiment and further includes a p-collector layer 42 inserted between the n-drift layer 27 and the drain electrode 28. The p-collector layer 42 is shared between the current detection device 21 and the main device 24. In the IGBT, a p-body region and a drain electrode are called p-base region and collector electrode, respectively. The second to eighth embodiments may have the p-collector layer 42 to yield an IGBT. In this way, even for a conductivity modulation semiconductor device, withstand voltage of the current detection device 21 becomes higher than withstand voltage of the main device 24 under reverse bias.
Tenth Embodiment
(73) FIG. 10 is a plan view illustrating a configuration of a semiconductor device having a current detection function according to a tenth embodiment. FIG. 11 is a cross-sectional view of the semiconductor device having a current detection function according to the tenth embodiment. As depicted in FIG. 11, the semiconductor device having the current detection function includes a main device 24 and a current detection device 21 separated from the main device 24. The current detection device 21 is formed in a current detecting structure region of the same substrate as the main device 24. Therefore, the current detection device 21 and the main device 24 share an n-drift layer 27, a p-collector layer 42, and a collector electrode 28.
(74) In FIG. 11, the main device 24 and the current detection device 21 are about the same size. However, actually, the surface area of the current detection device 21 is several tenths smaller than that of the main device 24. Therefore, reflecting the ratio of the surface areas, the current that flows through the current detection device 21 is several percent of that flowing through the main device 24. Detection of the current flowing through the current detection device 21 enables control of the main device 24 even when overcurrent flows through the main device 24.
(75) The structure of the main device 24 is explained. The main device 24 is formed in the main active region on the same semiconductor substrate as the current detection device 21 and has a first dummy trench IGBT structure 101. Multiple trenches are formed on a surface opposite to a surface where a collector electrode 28 of an n-drift layer 27 is formed. In the trenches, trench gate electrodes 84 and dummy trench electrodes 86 are formed where gate electrodes 26, electrodes made of polycrystalline silicone or the like, are implanted with a gate insulating film flanked by a trench and an electrode. The trench gate electrode 84 is made up of a trench gate structure unit that is electrically connected to a gate terminal G. The dummy trench electrode 86 is made up of a dummy trench structure unit that is not connected to the gate terminal G.
(76) On the surface of a region between the trench gate electrodes 84, a p-base region 32 is formed. In the p-base region 32, n.sup.+ source regions 38 are formed on the trench gate electrodes 84. On the entire substrate, interlayer insulator 40 is formed. The interlayer insulator includes an opening through which the p-base region 32 and the n.sup.+ source regions 38 contact an emitter electrode 25. In regions between the trench gate electrode 84 and the dummy trench electrode 86 and between the dummy trench electrodes 86, a p-type floating layer 82 is formed. The p-type floating layer 82 is separated from the emitter electrode 25 by the interlayer insulator 40 and is electrically isolated (floating) from the emitter electrode 25. The trench gate electrodes 84 of the main device 24 are electrically connected to each other and are connected to the gate terminal G. The dummy trench electrodes 86 are connected to the p-type floating layer 82 in a region that is not depicted in the drawing. In this way, potential of the main device 24 becomes stable.
(77) The structure of the current detection device 21 is explained. The current detection device 21 has a second dummy trench IGBT structure 102. Namely, the current detection device 21 is different from the main device 24 in that a p-type floating layer 81 contacts a current sensing electrode (emitter electrode) 22. Therefore, potential of the p-type floating layer 81 becomes identical to that of the emitter electrode 22 and is not electrically isolated from the emitter electrode 22.
(78) The dummy trench electrode 85 is electrically connected to the trench gate electrode 83 of the current detection device 21 and the trench gate electrode 84 of the main device 24. Accordingly, potential of the dummy trench electrodes 85 becomes identical to the gate terminal G. The emitter electrode 22 is separated from the emitter electrode 25 of the main device 24. As depicted in FIG. 10, each trench may be terminated in the main device 24 and the current detection device 21.
(79) According to the tenth embodiment, as the withstand voltage of the main device 24 and the current detection device 21 becomes higher, loads or currents do not build up in the current detection device 21 even if large surge voltage is caused by, for example, the switching operation of the IGBT. Therefore, even when overcurrent flows through the main device 24, the current detection device 21 is not destroyed and the current detection device 21 can detect the overcurrent flowing through the main device 24. As a result, operation can be stopped or a protection circuit is activated before the main device 24 is destroyed, whereby reliability of a device is improved.
Eleventh Embodiment
(80) FIG. 12 is a cross-sectional view of a semiconductor device having a current detection function according to an eleventh embodiment. As depicted in FIG. 12, according to the eleventh embodiment, the current detection device 21 has a third dummy trench IGBT structure 103 compared with the tenth embodiment. In the current detection device 21, the dummy trench electrodes 85 are not connected to the trench gate electrodes 83 and 84 but are connected to the p-type floating layer 81 in a region that is not depicted in the drawing. As a result, potential of the current detection device 21 becomes stable. The p-type floating layer 81 is also connected to the emitter electrode. Accordingly, potential of the p-type floating layer 81 becomes identical to potential of the emitter electrode 22, the p-type floating layer 81 not being electrically isolated from the emitter electrode 22. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twelfth Embodiment
(81) FIG. 13 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twelfth embodiment. In the twelfth embodiment, the current detection device 21 has a fourth dummy trench IGBT structure 104 compared with the tenth embodiment and the eleventh embodiment. In the current detection device 21, the dummy trench electrodes 85 are electrically connected to the emitter electrode 22. Therefore, the dummy trench electrodes 85 and the emitter electrode 22 have identical potential and thus, potential of the current detection device 21 becomes stable. The p-type floating layers 81 are separated from the emitter electrode 22 by the interlayer insulator 37. Thus, the p-type floating layers 81 are electrically isolated (floating) from the emitter electrode 22. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Thirteenth Embodiment
(82) FIG. 14 is a cross-sectional view of a semiconductor device having a current detection function according to a thirteenth embodiment. As depicted in FIG. 14, according to the thirteenth embodiment, the current detection device 21 has a fifth dummy trench IGBT structure 105 compared with the tenth to twelfth embodiments. In the current detection device 21, the dummy trench electrodes 85 are electrically connected to the emitter electrode 22. Accordingly, potential of the dummy trench electrodes 85 and the emitter electrode 22 becomes identical and thus, potential of the current detection device 21 becomes stable. The p-type floating layers 81 contact the emitter electrode 22. Thus potential of the p-type floating layers 81 and the emitter electrode 22 becomes identical and the p-type floating layers 81 are not electrically isolated from the emitter electrode 22. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Fourteenth Embodiment
(83) FIG. 15 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a fourteenth embodiment. As depicted in FIG. 15, according to the fourteenth embodiment, the current detection device 21 has a sixth dummy trench IGBT structure 106 compared with the tenth to thirteenth embodiments. In the current detection device 21, the dummy trench electrodes 85 are electrically connected to the trench electrodes 83 and 84. As a result, the dummy trench electrodes 85 and the gate terminal G have identical potential. The p-type floating layers 81 are separated from the emitter electrode 22 by the interlayer insulator 37 and thus, are electrically isolated (floating) from the emitter electrode 22. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Fifteenth Embodiment
(84) FIG. 16 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a fifteenth embodiment. As depicted in FIG. 16, in the fifteenth embodiment, the main device 24 has a seventh dummy trench IGBT structure 107 compared with the tenth embodiment. In the main device 24, a dummy trench electrode 86 is connected to a p-type floating layer 82. It is desirable for the dummy trench electrode 86 to be connected to a p-type floating layer 82 closer to an n.sup.+ source region 38 because the withstand voltage rises more. The p-type floating layer 82 is separated from the emitter electrode 25 by the interlayer insulator 40 and is connected to the dummy trench electrode 86. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Sixteenth Embodiment
(85) FIG. 17 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a sixteenth embodiment. As depicted in FIG. 17, in the sixteenth embodiment, the current detection device 21 has the third dummy trench IGBT structure 103 compared with the fifteenth embodiment. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Seventeenth Embodiment
(86) FIG. 18 is a cross-sectional view illustrating a semiconductor device having a current detection function according to the seventeenth embodiment. As depicted in FIG. 18, in the seventeenth embodiment, the current detection device 21 has the fourth dummy trench IGBT structure 104 compared with the fifteenth and sixteenth embodiments. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Eighteenth Embodiment
(87) FIG. 19 is a cross-sectional view illustrating a semiconductor device having a current detection function according to an eighteenth embodiment. As depicted in FIG. 19, in the eighteenth embodiment, the current detection device 21 has the fifth dummy trench IGBT structure 105 compared with the fifteenth to seventeen embodiments. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Nineteenth Embodiment
(88) FIG. 20 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a nineteenth embodiment. As depicted in FIG. 20, in the nineteenth embodiment, the current detection device 21 has the sixth dummy trench IGBT structure 106 compared with the fifteenth to eighteenth embodiments.
Twentieth Embodiment
(89) FIG. 21 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twentieth embodiment. As depicted in FIG. 21, in the twentieth embodiment, the main device 24 has the fourth dummy trench IGBT structure 104 compared with the tenth embodiment. A dummy trench electrode 86 of the main device 24 is electrically connected to the emitter electrode 25. As a result, potential of the main device 24 becomes stable. A p-type floating layer 82 is separated from the emitter electrode 25 by the interlayer insulator 40. Therefore, the p-type floating layer 82 is electrically isolated (floating) from the emitter electrode 25. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twenty-First Embodiment
(90) FIG. 22 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-first embodiment. As depicted in FIG. 22, in the twenty-first embodiment, the current detection device 21 has a third dummy trench IGBT structure 103 compared with the twentieth embodiment. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twenty-Second Embodiment
(91) FIG. 23 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-second embodiment. As depicted in FIG. 23, in the twenty-second embodiment, the current detection device 21 has the fifth dummy trench IGBT structure 105 compared with the twentieth and the twenty-first embodiments. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twenty-Third Embodiment
(92) FIG. 24 is a cross sectional view illustrating a semiconductor device having a current detection function according to a twenty-third embodiment. As depicted in FIG. 24, in the twenty-third embodiment, the main device 24 has the sixth dummy trench IGBT structure 106 compared with the tenth embodiment. A dummy trench electrode 86 of the main device 24 is connected to the trench gate electrodes 83 and 84. Consequently, potential of the dummy trench electrode 86 and the gate terminal G becomes identical. A p-type floating layer 82 is separated from the emitter electrode 25 by the interlayer insulator 40. Therefore, the p-type floating layer 82 is electrically isolated (floating) from the emitter electrode 25. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 21.
Twenty-Fourth Embodiment
(93) FIG. 25 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-fourth embodiment. As depicted in FIG. 25, in the twenty-fourth embodiment, the current detection device 21 has the third dummy trench IGBT structure 103 compared with the twenty-third embodiment. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twenty-Fifth Embodiment
(94) FIG. 26 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-fifth embodiment. As depicted in FIG. 26, in the twenty-fifth embodiment, the current detection device 21 has the fifth dummy trench IGBT structure 105 compared with the twenty-fourth embodiment. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twenty-Sixth Embodiment
(95) FIG. 27 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-sixth embodiment. As depicted in FIG. 27, in the twenty-sixth embodiment, the main device 24 has a trench IGBT structure 110 compared with the tenth embodiment. The main device 24 does not have a dummy trench electrode and has a structure similar to the current detection device 21 depicted in FIG. 8. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twenty-Seventh Embodiment
(96) FIG. 28 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-seventh embodiment. As depicted in FIG. 28, in the twenty-seventh embodiment, the current detection device 21 has the first dummy trench IGBT structure 101 compared with the twenty-sixth embodiment. A dummy trench electrode 85 of the current detection device 21 is connected to a p-type floating layer 81 in a region that is not depicted. As a result, potential of the current detection device 21 becomes stable. The p-type floating layer 81 is separated from the emitter electrode 22 by the interlayer insulator 37 and is electrically isolated (floating) from the emitter electrode 22. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twenty-Eighth Embodiment
(97) FIG. 29 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-eighth embodiment. As depicted in FIG. 29, in the twenty-eighth embodiment, the current detection device 21 has the third dummy trench IGBT structure 103 compared with the twenty-sixth and twenty-seventh embodiments. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Twenty-Ninth Embodiment
(98) FIG. 30 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a twenty-ninth embodiment. As depicted in FIG. 30, in the twenty-ninth embodiment, the current detection device 21 has the fourth dummy trench IGBT structure 104 compared with the twenty-sixth to twenty-eighth embodiments. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Thirtieth Embodiment
(99) FIG. 31 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a thirtieth embodiment. As depicted in FIG. 31, in the thirtieth embodiment, the current detection device 21 has the fifth dummy trench IGBT structure 105 compared with the twenty-sixth to twenty-ninth embodiments. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Thirty-First Embodiment
(100) FIG. 32 is a cross-sectional view illustrating a semiconductor device having a current detection function according to a thirty-first embodiment. As depicted in FIG. 32, in the thirty-first embodiment, the current detection device 21 has the sixth dummy trench IGBT structure 106 compared with the twenty-sixth to thirtieth embodiments. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
Thirty-Second Embodiment
(101) FIG. 33 is a cross-sectional view of a semiconductor device having a current detection function according to a thirty-second embodiment. As depicted in FIG. 33, in the thirty-second embodiment, the current detection device 21 has the seventh dummy trench IGBT structure 107 compared with the twenty-sixth to thirty-first embodiments. A dummy trench electrode 85 of the current detection device 21 is connected to a p-type floating layer 81. It is desirable for the dummy trench electrode 85 to be connected to a p-type floating layer 81 closer to an n.sup.+ source region 35 because the withstand voltage of the device rises more. The p-type floating layer 81 is separated from emitter electrode 22 by the interlayer insulator 37 and is connected to the dummy trench electrode 85. In this way, the withstand voltage of the current detection device 21 becomes higher than the main device 24.
EXAMPLE
(102) FIG. 34 is a diagram illustrating relationships between a device structure of IGBT and the withstand voltage of the device. In FIG. 34, the vertical axis indicates the device withstand voltage and the horizontal axis indicates the device structure of IGBT. The device structure of IGBT depicts where a dummy trench electrode and a p-type floating layer are connected.
(103) As depicted in FIG. 34, when a dummy trench electrode is not formed and a p-type floating layer is electrically isolated (floating) (when the main device 24 has a trench IGBT structure that is illustrated in FIGS. 27 to 32), the device withstand voltage is 1240V.
(104) In the case of the first dummy trench IGBT structure 101 applied to the main device 24 as depicted in FIG. 11 to FIG. 15 and to the current detection device 21 as depicted in FIG. 28, and in the case of the seventh dummy trench IGBT structure 107 applied to the main device 24 as depicted in FIG. 16 to FIG. 20 and to the current detection device 21 as depicted in FIG. 33, the device withstand voltage is 1280V.
(105) In the case of the fourth dummy trench IGBT structure 104 applied to the main device 24 as depicted in FIG. 21 to FIG. 23 and to the current detection device 21 as depicted in FIG. 13, FIG. 18, and FIG. 30, and in the case of the sixth dummy trench IGBT structure 106 applied to the main device 24 as depicted in FIG. 24 to FIG. 26 and to the current detection device 21 as depicted in FIG. 15, FIG. 20, and FIG. 32, the device withstand voltage is 1350V.
(106) In the case of the second dummy trench IGBT structure 102 applied to the current detection device 21 as depicted in FIG. 11, FIG. 16, FIG. 21, FIG. 24, and FIG. 27, in the case of the third dummy trench IGBT structure 103 applied to the current detection device 21 as depicted in FIG. 12, FIG. 17, FIG. 22, FIG. 25, and FIG. 29, and in the case of the fifth dummy trench IGBT structure 105 applied to the current detection device 21 as depicted in FIG. 14, FIG. 19, FIG. 23, FIG. 26, and FIG. 31, the device withstand voltage is 1370V.
(107) As explained above, in the tenth to thirty-second embodiments, it is noted that the withstand voltage of the current detection device 24 is higher than the main device 24. As a result, even when large surge voltage occurs because of, for example, a switching operation of the IGBT, loads and currents do not build up in the current detection device. Therefore, even if overcurrent flows through the main device, the current detection device is not destroyed and thus, the current detection device can detect overcurrent flowing through the main device. Consequently, an operation of the device can be stopped or a protection circuit can be activated before the main device is destroyed, thereby improving reliability of the device.
(108) The above exemplary embodiments may further be modified. For example, although a first conductivity type is an n-type and a second conductivity type is a p-type in the above embodiments, the first conductivity type may be a p-type and the second conductivity type may be an n-type. The main device 24 and the current detection device 21 may be formed separately on different semiconductor chips so that a semiconductor device with a current detection function includes two or more chips. In this case, the drain terminal (collector terminal) of the main device 24 and the drain terminal (collector terminal) of the current detection device 21 are electrically connected through external wiring.
INDUSTRIAL APPLICABILITY
(109) As explained above, a semiconductor device according to the invention is of use for a power semiconductor device, especially, for a MOSFET or IGBT for a vehicle.
