Patent ID: 8125004

Claim:
A field-effect semiconductor device comprising: (a) a main semiconductor region having a first and a second semiconductor layer of dis-similar semiconducting materials such that a two-dimensional carrier gas is generated in the first semiconductor layer along a heterojunction between the first and the second semiconductor layer, the main semiconductor region having a major surface; (b) a first and a second main electrode disposed in spaced-apart positions on the major surface of the main semiconductor region and electrically coupled to the two-dimensional carrier gas in the first semiconductor layer of the main semiconductor region; (c) a gate electrode disposed between, and spaced from, the first and the second main electrode on the major surface of the main semiconductor region for controlling conduction between the first and the second main electrode via the two-dimensional carrier gas layer; (d) a metal oxide semiconductor film disposed between the main semiconductor region and the gate electrode and having a conductivity type such that a depletion zone is normally created in the two-dimensional carrier gas layer through reduction of charge carriers; and (e) an insulating film disposed between the main semiconductor region and the gate electrode.