Patent ID: 8384152

Claim:
A semiconductor device comprising: a drain layer of a first conductivity type; a body layer of a second conductivity type formed on the drain layer, the body layer having a body region and a surface layer portion on the body region; a gate trench passing through the body layer so that the deepest portion thereof reaches the drain layer; a source region of the first conductivity type formed around the gate trench on the surface layer portion of the body layer; a gate insulating film formed on a bottom surface and a side surface of the gate trench; and a gate electrode embedded in the gate trench through the gate insulating film, an upper portion of the gate electrode encompassed by the source region being thinner than a lower portion of the gate electrode encompassed by the body region of the body layer excluding the source region, the bottom surface of the gate electrode and the upper surface of the drain layer being flush with each other, and the thickness of a portion of the gate insulating film sandwiched between the upper portion of the gate electrode and the source region being larger than the thickness of a portion of the gate insulating film sandwiched between the lower portion of the gate electrode and the body region.