Patent ID: 7485924

Claim:
A lateral double-diffused field effect transistor, comprising: a second conductivity-type body diffusion layer formed on a surface of a first conductivity-type semiconductor layer with use of substantially a rectangular pattern; a first conductivity-type source diffusion layer formed in a region of the body diffusion layer occupying a part of a surface of the body diffusion layer; a first conductivity-type drain diffusion layer formed in a region of the surface of the first conductivity-type semiconductor layer surrounding the body diffusion layer from a distance; and a gate electrode covering at least the surface of the semiconductor layer between the source diffusion layer and the drain diffusion layer through a gate insulating film, wherein the gate insulating film includes a first gate insulating film covering the source diffusion layer up to a region beyond a pattern of the body diffusion layer and a second gate insulating film having a film thickness larger than that of the first gate insulating film and covering a region closer to the drain diffusion layer than the region covered by the first gate insulating film, wherein a boundary between the first gate insulating film and the second gate insulating film is composed of a straight portion parallel to a side of the pattern of the body diffusion layer and a corner portion surrounding an vertex of the pattern of the body diffusion layer from a distance, and wherein a distance between the vertex of the pattern of the body diffusion layer and the corner portion of the boundary is equal to or smaller than a distance between the side of the pattern of the body diffusion layer and the straight portion of the boundary.