Patent ID: 7985987

Claim:
A field-effect semiconductor device comprising: (a) a main semiconductor region having a first semiconductor layer and a second semiconductor layer disposed on the first semiconductor layer, the second semiconductor layer having a higher bandgap than the first semiconductor layer, the first semiconductor layer including a two-dimensional carrier gas layer, the main semiconductor region having a first and a second opposite major surface and a first and a second recess formed in the first major surface of the main semiconductor region; (b) a first and a second main electrode disposed in the first and the second recess of the main semiconductor region and electrically coupled to the two-dimensional carrier gas layer 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 first 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; and (d) a metal oxide semiconductor film disposed between the gate electrode and the main semiconductor region, and having a conductivity type such that carrier concentration in the two-dimensional carrier gas layer is reduced.