Microelectronic structures embodying the present invention include a field effect transistor (FET) having highly conductive source/drain extensions. Formation of such highly conductive source/drain extensions includes forming a passivated recess which is back filled by epitaxial deposition of doped material to form the source/drain junctions. The recesses include a laterally extending region that underlies a portion of the gate structure. Such a lateral extension may underlie a sidewall spacer adjacent to the vertical sidewalls of the gate electrode, or may extend further into the channel portion of a FET such that the lateral recess underlies the gate electrode portion of the gate structure. In one embodiment the recess is back filled by an in-situ epitaxial deposition of a bilayer of oppositely doped material. In this way, a very abrupt junction is achieved that provides a relatively low resistance source/drain extension and further provides good off-state subthreshold leakage characteristics. Alternative embodiments can be implemented with a back filled recess of a single conductivity type.

A semiconductor structure is provided, comprising a substrate (130), a support structure (131), a base region (100), a gate stack, a spacer (240), and a source/drain region, wherein the gate stack is located above the base region (100), and the base region (100) is supported above the substrate (130) by the support structure (131), wherein the support structure (131) has a sigma-shaped lateral cross-section; an isolation structure (123) is formed below edges on both sides of the base region (100), wherein a portion of the isolation structure (123) is connected to the substrate (130); a cavity (112) is formed between the isolation structure (123) and the support structure (131); and a source/drain region is formed on both sides of the base region (100) and the isolation structure (123). Accordingly, a method for manufacturing the semiconductor structure is also provided.

The semiconductor device structures and methods for forming the same are provided. The semiconductor device structure includes a metal gate over a substrate. A first spacer is formed over sidewalls of the metal gate and having a first height. A second spacer is formed over the sidewalls of the metal gate and having a second height. The first height is higher than the second height. The first spacer is farther from the sidewalls of the metal gate than the second spacer. In addition, the semiconductor device structure includes a dielectric layer formed over the substrate to surround the first spacer and the metal gate.

A semiconductor device includes a substrate, a gate structure, a sidewall spacer, and an epitaxial layer. The gate structure is disposed on the substrate, and the substrate has at least one recess disposed adjacent to the gate structure. The sidewall spacer is disposed on at least two sides of the gate structure. The sidewall spacer includes a first spacer layer and a second spacer layer, and the first spacer layer is disposed between the gate structure and the second spacer layer. The epitaxial layer is disposed in the recess, and the recess is a circular shaped recess. A distance between an upmost part of the recess and the gate structure is less than a width of the sidewall spacer.

An integrated circuit structure include a semiconductor substrate, a gate stack over the semiconductor substrate, and a recess extending into the semiconductor substrate, wherein the recess is adjacent to the gate stack. A silicon germanium region is disposed in the recess, wherein the silicon germanium region has a first p-type impurity concentration. A silicon cap substantially free from germanium is overlying the silicon germanium region. The silicon cap has a second p-type impurity concentration greater than the first p-type impurity concentration.

A method for forming a semiconductor device includes steps as follows: Firstly, a semiconductor substrate having a circuit element with at least one spacer formed thereon is provided. Next, an acid treatment is performed on a surface of the spacer. A disposable layer is then formed on the circuit element and the spacer. Thereafter, an etching process is performed to form at least one recess in the semiconductor substrate adjacent to the circuit element. Subsequently, a selective epitaxial growth (SEG) process is performed to form an epitaxial layer in the recess.

A method for forming a semiconductor device comprising forming a sacrificial gate stack on a channel region of first layer of a substrate, forming a spacer adjacent to the sacrificial gate stack, forming a raised source/drain region on the first layer of the substrate adjacent to the spacer, forming a dielectric layer over the raised source/drain region, removing the sacrificial gate stack to expose the channel region of the first layer of the substrate, and implanting dopants in a second layer of the substrate to form an implant region in the second layer below the channel region of the first layer of the substrate, where the first layer of the substrate is arranged on the second layer of the substrate.

A semiconductor device comprises a first layer of a substrate arranged on a second layer of the substrate the second layer of the substrate including a doped III-V semiconductor material barrier layer, a gate stack arranged on a channel region of the first layer of a substrate, a spacer arranged adjacent to the gate stack on the first layer of the substrate, an undoped epitaxially grown III-V semiconductor material region arranged on the second layer of the substrate, and an epitaxially grown source/drain region arranged on the undoped epitaxially grown III-V semiconductor material region, and a portion of the first layer of the substrate.

Raised structures comprising overlying silicon layers formed by controlled selective epitaxial growth, and methods for forming such raised-structure on a semiconductor substrate are provided. The structures are formed by selectively growing an initial epitaxial layer of mono crystalline silicon on the surface of a semi conductive substrate, and forming a thin film of insulative material over the epitaxial layer. A second epitaxial layer is selectively, grown on the exposed surface of the initial epitaxially grown crystal layer, and a thin insulative film is deposited over the second epitaxial layer. Additional epitaxial layers are added as desired to provide a vertical structure of a desired height comprising multiple layers of single silicon crystals, each epitaxial layer have insulated sidewalls, with the uppermost epitaxial layer also with an insulated top surface.

A semiconductor device comprises a semiconductor substrate; a channel layer of at least one III-V semiconductor compound above the semiconductor substrate; a gate electrode above a first portion of the channel layer; a source region and a drain region above a second portion of the channel layer; and a dopant layer comprising at least one dopant contacting the second portion of the channel layer.