Patent ID: 7838904

Claim:
A semiconductor device comprising: a substrate; a semiconductor multilayer having a first nitride-based compound semiconductor layer provided over the substrate and a second nitride-based compound semiconductor layer provided over the first nitride-based compound semiconductor layer to have a band gap larger than that of the first nitride-based compound semiconductor layer; a source electrode and a drain electrode each provided to have at least a portion thereof in contact with the semiconductor multilayer, a concave portion provided on an upper surface of the semiconductor multilayer to be located between the source electrode and the drain electrode, and concaved in a thickness direction of the semiconductor multilayer; a gate electrode provided over the concave portion to cover an opening of the concave portion; and a p-type nitride-based compound semiconductor layer provided to cover the opening of the concave portion and to be located between the gate electrode and the semiconductor multilayer, wherein the p-type nitride-based compound semiconductor layer works as a part of a terminal for controlling a current between the source and the drain by applying a voltage, and a film thickness of a portion of the p-type nitride-based compound semiconductor layer located over a bottom surface of the concave portion is larger than a film thickness of a portion of the p-type nitride-based compound semiconductor layer located on the upper surface of the semiconductor multilayer.