Gates having air gaps therein, and methods of fabrication thereof, are disclosed herein. An exemplary gate includes a gate electrode and a gate dielectric. A first air gap is between and/or separates a first sidewall of the gate electrode from the gate dielectric, and a second air gap is between and/or separates a second sidewall of the gate electrode from the gate dielectric. A dielectric cap may be disposed over the gate electrode, and the dielectric cap may wrap a top of the gate electrode. The dielectric cap may fill a top portion of the first air gap and a top portion of the second air gap. The gate may be disposed between a first epitaxial source/drain and a second epitaxial source/drain, and a width of the gate is about the same as a distance between the first epitaxial source/drain and the second epitaxial source/drain.

A semiconductor device structure includes first nanostructures formed over a substrate. The structure also includes a first gate structure wrapping around the first nanostructures. The structure also includes a first source/drain epitaxial structure formed beside the first nanostructures. The structure also includes a first inner spacer between the first gate structure and the first source/drain epitaxial structure. The structure also includes second nanostructures formed over the first nanostructure. The structure also includes a second gate structure wrapping around the second nanostructures. The structure also includes a second source/drain epitaxial structure formed beside the second nanostructures. The structure also includes a second inner spacer between the second gate structure and the second source/drain epitaxial structure. A sidewall of the second inner spacer is spaced apart from a sidewall of the first inner spacer when viewed from above.

A device includes a substrate and insulation regions over a portion of the substrate. A first semiconductor region is between the insulation regions and having a first conduction band. A second semiconductor region is over and adjoining the first semiconductor region, wherein the second semiconductor region includes an upper portion higher than top surfaces of the insulation regions to form a semiconductor fin. The second semiconductor region also includes a wide portion and a narrow portion over the wide portion, wherein the narrow portion is narrower than the wide portion. The semiconductor fin has a tensile strain and has a second conduction band lower than the first conduction band. A third semiconductor region is over and adjoining a top surface and sidewalls of the semiconductor fin, wherein the third semiconductor region has a third conduction band higher than the second conduction band.

Embodiments of the present disclosure include contact structures and methods of forming the same. An embodiment is a method of forming a semiconductor device, the method including forming a contact region over a substrate, forming a dielectric layer over the contact region and the substrate, and forming an opening through the dielectric layer to expose a portion of the contact region. The method further includes forming a metal-silicide layer on the exposed portion of the contact region and along sidewalls of the opening; and filling the opening with a conductive material to form a conductive plug in the dielectric layer, the conductive plug being electrically coupled to the contact region.

Techniques are disclosed for improved integration of germanium (Ge)-rich p-MOS source/drain contacts to, for example, reduce contact resistance. The techniques include depositing the p-type Ge-rich layer directly on a silicon (Si) surface in the contact trench location, because Si surfaces are favorable for deposition of high quality conductive Ge-rich materials. In one example method, the Ge-rich layer is deposited on a surface of the Si substrate in the source/drain contact trench locations, after removing a sacrificial silicon germanium (SiGe) layer previously deposited in the source/drain locations. In another example method, the Ge-rich layer is deposited on a Si cladding layer in the contact trench locations, where the Si cladding layer is deposited on a functional p-type SiGe layer. In some cases, the Ge-rich layer comprises at least 50% Ge (and may contain tin (Sn) and/or Si) and is boron (B) doped at levels above 1E20 cm.sup.3.

A method for fabricating a semiconductor device is provided. The method includes forming a first fin-shaped pattern including an upper part and a lower part on a substrate, forming a second fin-shaped pattern by removing a part of the upper part of the first fin-shaped pattern, forming a dummy gate electrode intersecting with the second fin-shaped pattern on the second fin-shaped pattern, and forming a third fin-shaped pattern by removing a part of an upper part of the second fin-shaped pattern after forming the dummy gate electrode, wherein a width of the upper part of the second fin-shaped pattern is smaller than a width of the upper part of the first fin-shaped pattern and is greater than a width of an upper portion of the third fin-shaped pattern.

A hetero-channel FinFET device provides enhanced switching performance over a FinFET device having a silicon channel, and is easier to integrate into a fabrication process than is a FinFET device having a germanium channel. A FinFET device featuring the heterogeneous Si/SiGe channel includes a fin having a central region made of silicon and sidewall regions made of SiGe. A hetero-channel pFET device in particular has higher carrier mobility and less gate-induced drain leakage current than either a silicon device or a SiGe device. The hetero-channel FinFET permits the SiGe portion of the channel to have a Ge concentration in the range of about 25-40% and permits the fin height to exceed 40 nm while remaining stable.

After forming a first-side epitaxial semiconductor region and a second-side epitaxial semiconductor region on recessed surfaces of a semiconductor portion that are not covered by a gate structure, at least one dielectric layer is formed to cover the first-side and the second-side epitaxial semiconductor regions and the gate structure. A second-side contact opening is formed within the at least one dielectric layer to expose an entirety of the second-side epitaxial semiconductor region. The exposed second-side epitaxial semiconductor region can be replaced by a new second-side epitaxial semiconductor region having a composition different from the first-side epitaxial semiconductor region or can be doped by additional dopants, thus creating an asymmetric first-side epitaxial semiconductor region and a second-side epitaxial semiconductor region. Each of the first-side epitaxial semiconductor region and the second-side epitaxial semiconducting region can function as either a source or a drain for a transistor.

In a method for fabricating a field-effect transistor (FET) structure, forming a shallow trench isolation (STI) structure on a semiconductor substrate, wherein the STI structure includes dielectric structures that form one or more dielectric walled aspect ratio trapping (ART) trenches. The method further includes epitaxially growing a first semiconductor material on the semiconductor substrate and substantially filling at least one of the one or more ART trenches, and recessing the first semiconductor material down into the ART trenches selective to the dielectric structures, such that the upper surface of the first semiconductor material is below the upper surface of the dielectric structures. The method further includes epitaxially growing a second semiconductor material on top of the first semiconductor material and substantially filling the ART trenches to form a semiconductor fin that comprises an upper portion comprising the second semiconductor material and a lower portion comprising the first semiconductor material.

A semiconductor device includes a substrate, a fin structure disposed over the substrate and including a channel region and a source/drain region, a gate structure disposed over at least a portion of the fin structure, the channel region being beneath the gate structure and the source/drain region being outside of the gate structure, a strain material layer disposed over the source/drain region, the strain material layer providing stress to the first channel region, and a contact layer wrapping around the first strain material layer. A width of the source/drain region is smaller than a width of the channel region.