A semiconductor structure includes several semiconductor stacks over a substrate, and each of the semiconductor stacks extends in a first direction, wherein adjacent semiconductor stacks are spaced apart from each other in a second direction, which is different from the first direction. Each of the semiconductor stacks includes channel layers above the substrate and a gate structure across the channel layers. The channel layers are spaced apart from each other in the third direction. The gate structure includes gate dielectric layers around the respective channel layers, and a gate electrode along sidewalls of the gate dielectric layers and a top surface of the uppermost gate dielectric layer. The space in the third direction between the two lowermost channel layers is greater than the space in the third direction between the two uppermost channel layers in the same semiconductor stack.

A method includes providing a channel region and growing an oxide layer on the channel region. Growing the oxide layer includes introducing a first source gas providing oxygen and introducing a second source gas providing hydrogen. The second source gas being different than the first source gas. The growing the oxide layer is grown by bonding the oxygen to a semiconductor element of the channel region to form the oxide layer and bonding the hydrogen to the semiconductor element of the channel region to form a semiconductor hydride byproduct. A gate dielectric layer and electrode can be formed over the oxide layer.

A method for fabricating a semiconductor device includes forming a deposition-type interface layer over a substrate, converting the deposition-type interface layer into an oxidation-type interface layer, forming a high-k layer over the oxidation-type interface layer, forming a dipole interface on an interface between the high-k layer and the oxidation-type interface layer, forming a conductive layer over the high-k layer, and patterning the conductive layer, the high-k layer, the dipole interface, and the oxidation-type interface layer to form a gate stack over the 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.

Methods are provided to form pure silicon oxide layers on silicon-germanium (SiGe) layers, as well as an FET device having a pure silicon oxide interfacial layer of a metal gate structure formed on a SiGe channel layer of the FET device. For example, a method comprises growing a first silicon oxide layer on a surface of a SiGe layer using a first oxynitridation process, wherein the first silicon oxide layer comprises nitrogen. The first silicon oxide layer is removed, and a second silicon oxide layer is grown on the surface of the SiGe layer using a second oxynitridation process, which is substantially the same as the first oxynitridation process, wherein the second silicon oxide layer is substantially devoid of germanium oxide and nitrogen. For example, the first silicon oxide layer comprises a SiON layer and the second silicon oxide layer comprises a pure silicon dioxide layer.

A semiconductor device includes a fin structure, a two-dimensional (2D) material channel layer, a ferroelectric layer, and a metal layer. The fin structure extends from a substrate. The 2D material channel layer wraps around at least three sides of the fin structure. The ferroelectric layer wraps around at least three sides of the 2D material channel layer. The metal layer wraps around at least three sides of the ferroelectric layer.

Improved gate stack designs for Si and SiGe dual channel devices are provided. In one aspect, a method for forming a dual channel device includes: forming fins on a substrate, the fins including Si fins in combination with SiGe fins as dual channels of an analog device and a logic device, with the analog device and the logic device each having a Si fin and a SiGe fin; forming a silicon germanium oxide (SiGeOx) layer on the SiGe fins; annealing the SiGeOx layer to form a Si-rich layer on the SiGe fins via a reaction between SiGeOx and SiGe; and forming metal gates over the Si fins and over the Si-rich layer on the SiGe fins. A dual channel device is also provided.

A semiconductor device includes a first layer of a first semiconductor material disposed on a semiconductor substrate and a second layer of a second semiconductor material disposed on the first layer. The second semiconductor material is formed of an alloy that includes a first element and a second element. The first semiconductor material and the second semiconductor material are different. A gate structure is disposed on a first portion of the second layer. A surface region of a second portion of the second layer not covered by the gate structure has a higher concentration of the second element than an internal region of the second portion of the second layer, and the surface region surrounds the internal region.

A semiconductor device includes a fin structure extending along a first direction, a channel layer wrapping around a top surface and opposite sidewalls of the fin structure, a gate stack extending across the channel layer along a second direction perpendicular to the first direction, and a spacer on a top surface of the channel layer and a sidewall of the gate stack when viewed in a cross section taken along the first direction. The channel layer includes a two-dimensional material. The gate stack includes a ferroelectric layer.

A method includes providing a channel region and growing an oxide layer on the channel region. Growing the oxide layer includes introducing a first source gas providing oxygen and introducing a second source gas providing hydrogen. The second source gas being different than the first source gas. The growing the oxide layer is grown by bonding the oxygen to a semiconductor element of the channel region to form the oxide layer and bonding the hydrogen to the semiconductor element of the channel region to form a semiconductor hydride byproduct. A gate dielectric layer and electrode can be formed over the oxide layer.