Abstract: A semiconductor device and methods of forming the same are disclosed. The semiconductor device includes a substrate, first and second source/drain (S/D) regions, a channel between the first and second S/D regions, a gate engaging the channel, and a contact feature connecting to the first S/D region. The contact feature includes first and second contact layers. The first contact layer has a conformal cross-sectional profile and is in contact with the first S/D region on at least two sides thereof. In embodiments, the first contact layer is in direct contact with three or four sides of the first S/D region so as to increase the contact area. The first contact layer includes one of a semiconductor-metal alloy, an III-V semiconductor, and germanium.

Abstract: A method includes forming a gate stack over a semiconductor region, and forming a first gate spacer on a sidewall of the gate stack. The first gate spacer includes an inner sidewall spacer, and a dummy spacer portion on an outer side of the inner sidewall spacer. The method further includes removing the dummy spacer portion to form a trench, and forming a dielectric layer to seal a portion of the trench as an air gap. The air gap and the inner sidewall spacer in combination form a second gate spacer. A source/drain region is formed to have a portion on an outer side of the second gate spacer.

Abstract: A semiconductor device having a first region and a second region is provided. The first region has a first protruding structure and a second protruding structure. The second region has a third protruding structure and a fourth protruding structure. First, second, third, and fourth epi-layers are formed on the first, second, third, and fourth protruding structures, respectively. The first and second epi-layers are covered with a first photoresist layer while leaving the third and fourth epi-layers exposed. A dielectric layer is formed over the first photoresist layer and over the third and fourth epi-layers. A portion of the dielectric layer is covered with a second photoresist layer. The portion of the dielectric layer is formed over the third and fourth epi-layers. Portions of the dielectric layer not protected by the first and second photoresist layers are etched. The first and second photoresist layers are removed.

Abstract: A semiconductor device having a first region and a second region is provided. The first region has a first protruding structure and a second protruding structure. The second region has a third protruding structure and a fourth protruding structure. First, second, third, and fourth epi-layers are formed on the first, second, third, and fourth protruding structures, respectively. The first and second epi-layers are covered with a first photoresist layer while leaving the third and fourth epi-layers exposed. A dielectric layer is formed over the first photoresist layer and over the third and fourth epi-layers. A portion of the dielectric layer is covered with a second photoresist layer. The portion of the dielectric layer is formed over the third and fourth epi-layers. Portions of the dielectric layer not protected by the first and second photoresist layers are etched. The first and second photoresist layers are removed.

Abstract: A method includes forming a semiconductor fin over a substrate; forming a helmet stack on a top surface of the semiconductor fin; forming a spacer layer over the helmet stack and on opposite sidewalls of the semiconductor fin; and etching the helmet layer and the spacer layer to expose the top surface and the sidewalls of the semiconductor fin.

Abstract: A semiconductor device includes a substrate, a bottom semiconductor fin, at least one sidewall structure, a top semiconductor fin, and a gate structure. The bottom semiconductor fin is disposed on the substrate. The sidewall structure protrudes from the semiconductor fin. The top semiconductor fin is disposed on the bottom semiconductor fin. The top semiconductor fin includes a channel portion and at least one source/drain portion. The source/drain portion is disposed between the channel portion and the sidewall structure. The gate structure covers the channel portion of the top semiconductor fin.

Abstract: A semiconductor device includes a substrate, a bottom semiconductor fin, at least one sidewall structure, a top semiconductor fin, and a gate structure. The bottom semiconductor fin is disposed on the substrate. The sidewall structure protrudes from the semiconductor fin. The top semiconductor fin is disposed on the bottom semiconductor fin. The top semiconductor fin includes a channel portion and at least one source/drain portion. The source/drain portion is disposed between the channel portion and the sidewall structure. The gate structure covers the channel portion of the top semiconductor fin.

Abstract: In a method for manufacturing a semiconductor device, a gate structure is formed over a channel layer and an isolation insulating layer. A first sidewall spacer layer is formed on a side surface of the gate structure. A sacrificial layer is formed so that an upper portion of the gate structure with the first sidewall spacer layer is exposed from the sacrificial layer and a bottom portion of the gate structure with the first sidewall spacer layer is embedded in the first sacrificial layer. A space is formed between the bottom portion of the gate structure and the sacrificial layer by removing at least part of the first sidewall spacer layer. After the first sidewall spacer layer is removed, an air gap is formed between the bottom portion of the gate structure and the sacrificial layer by forming a second sidewall spacer layer over the gate structure.

Abstract: A method for forming a semiconductor device structure is provided. The method includes providing a semiconductor substrate, a gate structure, a first doped structure, a second doped structure, and a dielectric layer. The method includes forming a through hole in the dielectric layer. The method includes performing a physical vapor deposition process to deposit a first metal layer over the first doped structure exposed by the through hole. The method includes reacting the first metal layer with the first doped structure to form a metal semiconductor compound layer between the first metal layer and the first doped structure. The method includes removing the first metal layer. The method includes performing a chemical vapor deposition process to deposit a second metal layer in the through hole. The method includes forming a conductive structure in the through hole and over the second metal layer.

Abstract: Various transistors, such as horizontal gate-all-around transistors, and methods of fabricating such are disclosed herein. An exemplary transistor includes a first nanowire and a second nanowire that include a first semiconductor material, a gate that wraps a channel region of the first nanowire and the second nanowire, and source/drain feature that wraps source/drain regions of the first nanowire and the second nanowire. The source/drain feature includes a second semiconductor material that is configured differently than the first semiconductor material. In some implementations, the transistor further includes a fin-like semiconductor layer disposed over a substrate. The first nanowire and the second nanowire are disposed over the fin-like semiconductor layer, such that the first nanowire, the second nanowire, and the fin-like semiconductor layer extend substantially parallel to one another along the same length-wise direction.

Abstract: A method includes forming a gate stack over a semiconductor region, depositing an impurity layer over the semiconductor region, and depositing a metal layer over the impurity layer. An annealing is then performed, wherein the elements in the impurity layer are diffused into a portion of the semiconductor region by the annealing to form a source/drain region, and wherein the metal layer reacts with a surface layer of the portion of the semiconductor region to form a source/drain silicide region over the source/drain region.

Abstract: In a method of manufacturing a semiconductor device, a support layer is formed over a substrate. A patterned semiconductor layer made of a first semiconductor material is formed over the support layer. A part of the support layer under a part of the semiconductor layer is removed, thereby forming a semiconductor wire. A semiconductor shell layer made of a second semiconductor material different from the first semiconductor material is formed around the semiconductor wire.

Abstract: A semiconductor device having a first region and a second region is provided. The first region has a first protruding structure and a second protruding structure. The second region has a third protruding structure and a fourth protruding structure. First, second, third, and fourth epi-layers are formed on the first, second, third, and fourth protruding structures, respectively. The first and second epi-layers are covered with a first photoresist layer while leaving the third and fourth epi-layers exposed. A dielectric layer is formed over the first photoresist layer and over the third and fourth epi-layers. A portion of the dielectric layer is covered with a second photoresist layer. The portion of the dielectric layer is formed over the third and fourth epi-layers. Portions of the dielectric layer not protected by the first and second photoresist layers are etched. The first and second photoresist layers are removed.

Abstract: Various semiconductor devices, such as horizontal gate-all-around devices, and methods of fabricating such are disclosed herein. An exemplary semiconductor device includes a fin structure having a channel region disposed between a first source/drain region and a second source/drain region. The fin structure includes a first nanowire and a second nanowire disposed in the channel region, the first source/drain region, and the second source/drain region. The fin structure further includes an epitaxial layer that wraps the first nanowire and the second nanowire in the first source/drain region and the second source/drain region. A gate is disposed over the channel region of the fin structure, such that the gate wraps the first nanowire and the second nanowire in the channel region. In some implementations, the first nanowire, the second nanowire, and the epitaxial layer combine to have a vertical bar-like shape in the first source/drain region and the second source/drain region.

Abstract: A semiconductor device and methods of forming the same are disclosed. The semiconductor device includes a substrate, first and second source/drain(S/D) regions, a channel between the first and second S/D regions, a gate engaging the channel, and a contact feature connecting to the first S/D region. The contact feature includes first and second contact layers. The first contact layer has a conformal cross-sectional profile and is in contact with the first S/D region on at least two sides thereof. In embodiments, the first contact layer is in direct contact with three or four sides of the first S/D region so as to increase the contact area. The first contact layer includes one of a semiconductor-metal alloy, an III-V semiconductor, and germanium.

Abstract: A method of forming a semiconductor device includes forming first and second fin structures on a substrate and a patterned polysilicon structure on first portions of the first and second fin structures. The method further includes depositing an insulating layer on second portions of the first and second fin structures and on the patterned polysilicon structure, which may be followed by selectively removing the insulating layer from the second portions and patterning a first hard mask layer on the second portion of the second fin structure. The method also includes growing a first epitaxial region on the second portion of the first fin structure, removing the patterned first hard mask layer from the second portion of the second fin structure, patterning a second hard mask layer on the first epitaxial region, and growing a second epitaxial region on the second portion of the second fin structure.

Abstract: A method of forming a semiconductor device includes forming first and second fin structures on a substrate and a patterned polysilicon structure on first portions of the first and second fin structures. The method further includes depositing an insulating layer on second portions of the first and second fin structures and on the patterned polysilicon structure, which may be followed by selectively removing the insulating layer from the second portions and patterning a first hard mask layer on the second portion of the second fin structure. The method also includes growing a first epitaxial region on the second portion of the first fin structure, removing the patterned first hard mask layer from the second portion of the second fin structure, patterning a second hard mask layer on the first epitaxial region, and growing a second epitaxial region on the second portion of the second fin structure.

Abstract: A semiconductor device and methods of forming the same are disclosed. The semiconductor device includes a substrate, first and second source/drain (S/D) regions, a channel between the first and second S/D regions, a gate engaging the channel, and a contact feature connecting to the first S/D region. The contact feature includes first and second contact layers. The first contact layer has a conformal cross-sectional profile and is in contact with the first S/D region on at least two sides thereof. In embodiments, the first contact layer is in direct contact with three or four sides of the first S/D region so as to increase the contact area. The first contact layer includes one of a semiconductor-metal alloy, an III-V semiconductor, and germanium.

Abstract: An embodiment high electron mobility transistor (HEMT) includes a gate electrode over a semiconductor substrate and a multi-layer semiconductor cap over the semiconductor substrate and adjacent the gate electrode. The multi-layer semiconductor cap includes a first semiconductor layer and a second semiconductor layer comprising a different material than the first semiconductor layer. The first semiconductor layer is laterally spaced apart from the gate electrode by a first spacing, and the second semiconductor layer is spaced apart from the gate electrode by a second spacing greater than the first spacing.

Abstract: According to an exemplary embodiment, a method of forming a fin structure is provided. The method includes the following operations: etching a first dielectric layer to form at least one recess and a first core portion of a fin core; form an oxide layer as a shallow trench isolation layer in the recess; etching back the oxide layer to expose a portion of the fin core; and forming a fin shell to cover a sidewall of the exposed portion of the fin core.