A FinFET including a gate stack, a semiconductor fin embedded in the gate stack, a source and a drain disposed is provided. The semiconductor fin extends along a widthwise direction of the gate stack and has a first concave and a second concave exposed at sidewalls of the gate stack respectively. The source and drain are disposed at two opposite sides of the gate stack. The source includes a first portion in contact with and embedded in the first concave. The drain includes a second portion in contact with and embedded in the second concave. The first portion and the second portion are covered by the gate stack.

A device includes a first semiconductor strip protruding from a substrate, a second semiconductor strip protruding from the substrate, an isolation material surrounding the first semiconductor strip and the second semiconductor strip, a nanosheet structure over the first semiconductor strip, wherein the nanosheet structure is separated from the first semiconductor strip by a first gate structure including a gate electrode material, wherein the first gate structure partially surrounds the nanosheet structure, and a first semiconductor channel region and a semiconductor second channel region over the second semiconductor strip, wherein the first semiconductor channel region is separated from the second semiconductor channel region by a second gate structure including the gate electrode material, wherein the second gate structure extends on a top surface of the second semiconductor strip.

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.

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 structure is provided. The semiconductor device structure includes a semiconductor substrate. The semiconductor device structure includes a gate stack over the semiconductor substrate. The semiconductor device structure includes spacers over opposite sidewalls of the gate stack. The spacers and the gate stack surround a recess over the gate stack. The semiconductor device structure includes a first insulating layer over the gate stack and an inner wall of the recess. The semiconductor device structure includes a second insulating layer over the first insulating layer. Materials of the first insulating layer and the second insulating layer are different, and a first thickness of the first insulating layer is less than a second thickness of the second insulating layer.

Techniques are disclosed for forming transistor devices having reduced parasitic contact resistance relative to conventional devices. The techniques can be implemented, for example, using a standard contact stack such as a series of metals on, for example, silicon or silicon germanium (SiGe) source/drain regions. In accordance with one example such embodiment, an intermediate boron doped germanium layer is provided between the source/drain and contact metals to significantly reduce contact resistance. Numerous transistor configurations and suitable fabrication processes will be apparent in light of this disclosure, including both planar and non-planar transistor structures (e.g., FinFETs), as well as strained and unstrained channel structures. Graded buffering can be used to reduce misfit dislocation. The techniques are particularly well-suited for implementing p-type devices, but can be used for n-type devices if so desired.

A semiconductor structure includes a substrate, first gate structures and second gate structures over the substrate, third epitaxial semiconductor features proximate the first gate structures, and fourth epitaxial semiconductor features proximate the second gate structures. The first gate structures have a greater pitch than the second gate structures. The third and fourth epitaxial semiconductor features are at least partially embedded in the substrate. A first proximity of the third epitaxial semiconductor features to the respective first gate structures is smaller than a second proximity of the fourth epitaxial semiconductor features to the respective second gate structures. In an embodiment, a first depth of the third epitaxial semiconductor features embedded into the substrate is greater than a second depth of the fourth epitaxial semiconductor features embedded into the substrate.

An integrated circuit structure includes a gate stack over a semiconductor substrate, and an opening extending into the semiconductor substrate, wherein the opening is adjacent to the gate stack. A first silicon germanium region is disposed in the opening, wherein the first silicon germanium region has a first germanium percentage. A second silicon germanium region is over the first silicon germanium region. The second silicon germanium region comprises a portion in the opening. The second silicon germanium region has a second germanium percentage greater than the first germanium percentage. A silicon cap substantially free from germanium is over the second silicon germanium region.