Patent ID: 8188538

Claim:
A semiconductor device, comprising: a semiconductor layer of a first conductivity type made of SiC having a first Si surface; a gate trench dug down from the first Si surface of the semiconductor layer such that the gate trench has a bottom surface parallel to the first Si surface and a side surface orthogonal to the first Si surface, the bottom surface being a second Si surface; a body region of a second conductivity type formed in the semiconductor layer and defining one part of the side surface of the gate trench; a source region of the first conductivity type formed on a surface layer portion of the body region and defining another part of the side surface of the gate trench; a drain region of the first conductivity type formed on an opposite side of the source region from the body region and defining the bottom surface of the gate trench; a gate insulating film including an insulating film bottom portion formed on the bottom surface of the gate trench and an insulating film side portion formed on the side surface of the gate trench, the insulating film bottom portion and the insulating film side portion intersecting each other and having respective uniform thicknesses; and a gate electrode embedded in the gate trench through the gate insulating film, wherein the ratio of the thickness of the insulating film bottom portion to the thickness of the insulating film side portion is between 0.3 and 1.0.