An oxide semiconductor device has an improved withstand voltage when an inverse voltage is applied, while suppressing diffusion of different types of materials to a Schottky interface. The oxide semiconductor device includes an n-type gallium oxide epitaxial layer, p-type oxide semiconductor layers of an oxide that is a different material from the material for the gallium oxide epitaxial layer, a dielectric layer formed to cover at least part of a side surface of the oxide semiconductor layer, an anode electrode, and a cathode electrode. Hetero pn junctions are formed between the lower surfaces of the oxide semiconductor layers and a gallium oxide substrate or between the lower surfaces of the oxide semiconductor layers and the gallium oxide epitaxial layer.

Devices, and methods of forming such devices, having a material that is semimetal when in bulk but is a semiconductor in the devices are described. An example structure includes a substrate, a first source/drain contact region, a channel structure, a gate dielectric, a gate electrode, and a second source/drain contact region. The substrate has an upper surface. The channel structure is connected to and over the first source/drain contact region, and the channel structure is over the upper surface of the substrate. The channel structure has a sidewall that extends above the first source/drain contact region. The channel structure comprises a bismuth-containing semiconductor material. The gate dielectric is along the sidewall of the channel structure. The gate electrode is along the gate dielectric. The second source/drain contact region is connected to and over the channel structure.

Devices, and methods of forming such devices, having a material that is semimetal when in bulk but is a semiconductor in the devices are described. An example structure includes a substrate, a first source/drain contact region, a channel structure, a gate dielectric, a gate electrode, and a second source/drain contact region. The substrate has an upper surface. The channel structure is connected to and over the first source/drain contact region, and the channel structure is over the upper surface of the substrate. The channel structure has a sidewall that extends above the first source/drain contact region. The channel structure comprises a bismuth-containing semiconductor material. The gate dielectric is along the sidewall of the channel structure. The gate electrode is along the gate dielectric. The second source/drain contact region is connected to and over the channel structure.

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.

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.

A transistor includes a gate electrode with multiple metals distributed along the width of the gate electrode. Each of the metals in the gate electrode has different work functions. Such a compound gate provides higher linearity when, e.g., operated as a radio frequency transistor.

A transistor includes a gate electrode with multiple metals distributed along the width of the gate electrode. Each of the metals in the gate electrode has different work functions. Such a compound gate provides higher linearity when, e.g., operated as a radio frequency transistor.

A copper plasma etching method according an exemplary embodiment includes: placing a substrate on a susceptor in a process chamber of a plasma etching apparatus; supplying an etching gas that include hydrogen chloride into the process chamber; plasma-etching a conductor layer that include copper in the substrate; and maintaining a temperature of the susceptor at 10 C. or less during the plasma-etching.

A copper plasma etching method according an exemplary embodiment includes: placing a substrate on a susceptor in a process chamber of a plasma etching apparatus; supplying an etching gas that include hydrogen chloride into the process chamber; plasma-etching a conductor layer that include copper in the substrate; and maintaining a temperature of the susceptor at 10 C. or less during the plasma-etching.

A method of manufacturing a semiconductor device includes forming a channel layer on a substrate, forming a mask on the channel layer, surface-treating an exposed surface of the channel layer exposed from the mask, forming an electrode on the exposed surface of the channel layer, and removing the mask. The channel layer includes a two-dimensional material, and the surface-treating of the exposed surface of the channel layer includes surface-treating the exposed surface of the channel layer with HCl.