Patent ID: 8178920

Claim:
A semiconductor device comprising: a base body formed of semiconductor material, the base body having a trench formed from the top surface thereof; a body region provided on the top surface side of the base body; a source region provided on the top surface side of the body region; a drain region provided on the bottom surface side of the base body; a drift layer provided in the base body between the source region and the drain region; a highly doped layer forming at least part of the drain region; a gate insulator film formed of insulating material provided at least on sidewall surfaces of the trench; and a gate electrode provided in the trench with the gate insulator film provided at least between the sidewall surfaces of the trench, wherein a product of a value of an insulation breakdown electric field strength and a value of a relative permittivity of the semiconductor material forming the base body is larger than a product of a normal value of an insulation breakdown electric field strength and a value of a relative permittivity of the insulating material forming the gate insulator film, wherein the trench penetrates the base body and the drift layer and reaches the highly doped layer on the drain region side, wherein a section of the trench deeper than the gate electrode is filled with an insulator having a normal value of an insulation breakdown electric field strength equal to or higher than the value of the insulation breakdown electric field strength of the semiconductor material of the base body, wherein the insulator at the bottom end of the gate electrode is thicker than the drift layer, wherein the sidewall surfaces of the trench located below the gate electrode is inclined to form a trapezoidal profile, and wherein the semiconductor material forming the base body is SiC, and each of the gate insulator film and the insulator filling the trench is SiO 2 .