Patent ID: 9306027
Filing Date: 2016-04-05
CPC Classification: H01L

Claim Text:
1. A semiconductor device comprising: a first nitride semiconductor layer formed over a substrate; a second nitride semiconductor layer formed over the first nitride semiconductor layer, and wider in band gap than the first nitride semiconductor layer; a trench formed in the second nitride semiconductor layer, the trench penetrating through the second nitride semiconductor layer and reaching the first nitride semiconductor layer at a bottom surface thereof, a first insulation film formed over the second nitride semiconductor layer to surround the trench; a gate insulation film being formed over the first insulation film and being formed on a side surface and the bottom surface of the trench; a gate electrode formed on the gate insulation film to overlap with the first insulation film; and a first electrode and a second electrode formed over the second nitride semiconductor layer on the opposite sides of the gate electrode, respectively, wherein the first insulation film has a first silicon nitride film in contact with the second nitride semiconductor layer, and a second silicon nitride film formed over the first silicon nitride film in contact with the gate insulating film, wherein the second silicon nitride film is larger in composition ratio of silicon (Si) than the first silicon nitride film, wherein the first silicon nitride film is larger in composition ratio of nitrogen (N) than the second silicon nitride film, and wherein a portion of the gate electrode is provided at least over the second silicon nitride film.