Patent ID: 8907349

Claim:
A semiconductor device including a field-effect transistor, the field-effect transistor comprising: (a) a channel layer composed of a first nitride semiconductor layer; (b) a spacer layer composed of a second nitride semiconductor layer formed on the channel layer; (c) an electron supply layer composed of a third nitride semiconductor layer formed on the spacer layer; (d) a source electrode formed on the electron supply layer; (e) a drain electrode formed on the electron supply layer and separated from the source electrode; (f) a p-type cap layer formed on the electron supply layer sandwiched between the source electrode and the drain electrode, wherein the electron supply layer between the spacer layer and the p-type cap layer is undoped; and (g) a gate electrode formed on the p-type cap layer, the spacer layer having a band-gap larger than that of the electron supply layer.