A method of manufacturing a semiconductor device includes: performing a first etching operation to form a first trench in a semiconductor substrate; forming a doped region to on a first sidewall of the first trench; performing a second etching operation on the first trench to form a second trench in the semiconductor substrate; depositing a dielectric material in the first and second trenches to form an isolation structure, wherein the isolation structure defines a channel region of the semiconductor device from a top-view perspective; and depositing a dielectric layer on the semiconductor substrate over the doped region and the channel region.

A method for manufacturing a semiconductor device includes forming a plurality of fins on a substrate, wherein each fin of the plurality of fins includes silicon germanium. A layer of silicon germanium oxide is deposited on the plurality of fins, and a first thermal annealing process is performed to convert outer regions of the plurality of fins into a plurality of silicon portions. Each silicon portion of the plurality of silicon portions is formed on a silicon germanium core portion. The method further includes forming a plurality of source/drain regions on the substrate, and depositing a layer of germanium oxide on the plurality of source/drain regions. A second thermal annealing process is performed to convert outer regions of the plurality of source/drain regions into a plurality of germanium condensed portions.

Semiconductor devices including a silicided substrate contact are described. In one example, a semiconductor device comprises a semiconductor substrate and a heterojunction structure over the semiconductor substrate, where the heterojunction structure includes a III-N buffer layer over the semiconductor substrate and a III-N barrier layer over the III-N buffer layer. A substrate contact extends through the heterojunction structure and to the semiconductor substrate, where the substrate contact includes a silicide layer contacting the semiconductor substrate.

A field-effect transistor (FET) and a radio-frequency module are provided comprising an active region comprising a source region, a drain region, a body region disposed between the source region and the drain region, a first body extension portion in contact with the body region, a second body extension portion in contact with the body region, and a body contact region in contact with the first extension portion and the second extension portion; and a gate disposed on a top surface of the body region. A die is also provided comprising two or more such FETs.