Abstract: Gallium nitride based RF transistor amplifiers include a semiconductor structure having a gallium nitride based channel layer and a gallium nitride based barrier layer thereon, and are configured to operate at a specific direct current drain-to-source bias voltage. These amplifiers are configured to have a normalized drain-to-gate capacitance at the direct current drain-to-source bias voltage, and to have a second normalized drain-to-gate capacitance at two-thirds the direct current drain-to-source bias voltage, where the second normalized drain-to-gate capacitance is less than twice the first normalized drain-to-gate capacitance.

Abstract: A semiconductor device includes a semiconductor layer structure that includes silicon carbide, a gate dielectric layer on the semiconductor layer structure, and a gate electrode on the gate dielectric layer opposite the semiconductor layer structure. In some embodiments, a periphery of a portion of the gate dielectric layer that underlies the gate electrode is thicker than a central portion of the gate dielectric layer, and a lower surface of the gate electrode has recessed outer edges such as rounded and/or beveled outer edges.