Semiconductor contact structures, a semiconductor device including the semiconductor contact structures, and a method for forming the same are disclosed. In an embodiment, a semiconductor device includes a channel layer on a substrate; an interface layer on the channel layer, the interface layer including titanium (Ti), the interface layer contacting the channel layer; and a contact metal layer over the interface layer, the contact metal layer including aluminum silicon copper alloy (AlSiCu).

The disclosed technology relates generally to semiconductor processing and more particularly to a method of forming a vertical field-effect transistor device. According to an aspect, a method of forming a vertical field-effect transistor device comprises forming on a substrate a vertical semiconductor structure protruding above the substrate and comprising a lower source/drain portion, an upper source/drain portion and a channel portion arranged between the lower source/drain portion and the upper source/drain portion. The method additionally comprises forming on the channel portion an epitaxial semiconductor stressor layer enclosing the channel portion, wherein the stressor layer and the channel portion are lattice mismatched, forming an insulating layer and a sacrificial structure, wherein the sacrificial structure encloses the channel portion with the stressor layer formed thereon and wherein the insulating layer embeds the semiconductor structure and the sacrificial structure, forming in the insulating layer an opening exposing a surface portion of the sacrificial structure, and etching the sacrificial structure through the opening in the insulating layer, thereby forming a cavity exposing the stressor layer enclosing the channel portion. The method further comprises, subsequent to etching the sacrificial structure, etching the stressor layer in the cavity, and subsequent to etching the stressor layer, forming a gate stack in the cavity, wherein the gate stack encloses the channel portion of the vertical semiconductor structure.

A transistor includes a silicon germanium layer, a gate stack, and source and drain features. The silicon germanium layer has a channel region. The silicon germanium layer has a first silicon-to-germanium ratio. The gate stack is disposed over the channel region of the silicon germanium layer and includes a silicon germanium oxide layer over and in contact with the channel region of the silicon germanium layer, a high- dielectric layer over the silicon germanium oxide layer, and a gate electrode over the high- dielectric layer. The silicon germanium oxide layer has a second silicon-to-germanium ratio, and the second silicon-to-germanium ratio is substantially the same as the first silicon-to-germanium ratio.

A method of fabricating a semiconductor device includes forming a fin structure on a substrate, forming a channel layer on a sidewall and a top surface of the fin structure, and forming a gate stack over the channel layer. The channel layer includes a two-dimensional (2D) material. The gate stack includes a ferroelectric layer.

In a method of manufacturing a semiconductor device, a single crystal oxide layer is formed over a substrate. After the single crystal oxide layer is formed, an isolation structure to define an active region is formed. A gate structure is formed over the single crystal oxide layer in the active region. A source/drain structure is formed.

A method of removing an oxide layer is provided. A metal layer is deposited over an oxide layer formed at a top surface of a germanium substrate. A metal oxide layer is deposited over the metal layer. The metal oxide layer includes a same metal material as the metal layer. The metal layer and the oxide layer are reacted and combined with the metal oxide layer to form a dielectric layer during an anneal process. During the anneal process, the oxide layer is reacted with the metal layer and removed.

A solar cell comprising a bulk germanium silicon growth substrate; a diffused photoactive junction in the germanium silicon substrate; and a sequence of subcells grown over the substrate, with the first grown subcell either being lattice matched or lattice mis-matched to the growth substrate.

A transistor comprises a substrate, a pair of spacers on the substrate, a gate dielectric layer on the substrate and between the pair of spacers, a gate electrode layer on the gate dielectric layer and between the pair of spacers, an insulating cap layer on the gate electrode layer and between the pair of spacers, and a pair of diffusion regions adjacent to the pair of spacers. The insulating cap layer forms an etch stop structure that is self aligned to the gate and prevents the contact etch from exposing the gate electrode, thereby preventing a short between the gate and contact. The insulator-cap layer enables self-aligned contacts, allowing initial patterning of wider contacts that are more robust to patterning limitations.

Example embodiments relate to germanium nanowire fabrication. One embodiment includes a method of forming a semiconductor device that includes at least one Ge nanowire. The method includes providing a semiconductor structure that includes at least one, the at least one fin including a stack of at least one Ge layer alternative with SiGe layers. The method also includes at least partially oxidizing the SiGe layer into SiGeO.sub.x. Further, the method includes capping the fin with a dielectric material. In addition, the method includes annealing. Still further, the method includes selectively removing the dielectric material and the SiGeO.sub.x.

A transistor includes a channel region, a gate stack, and source and drain structures. The channel region comprises silicon germanium and has a first silicon-to-germanium ratio. The gate stack is over the channel region and comprises a silicon germanium oxide layer over the channel region, a high- dielectric layer over the silicon germanium oxide layer, and a gate electrode over the high- dielectric layer. The silicon germanium oxide layer has a second silicon-to-germanium ratio. The second silicon-to-germanium ratio is substantially the same as the first silicon-to-germanium ratio. The channel region is between the source and drain structures.