Patent ID: 8125005

Claim:
A semiconductor device having a transistor, the semiconductor device comprising: a semiconductor layer; a semiconductor region of a first conductivity type, which is defined on the surface of the semiconductor layer; a semiconductor region of a second conductivity type, which is defined on the surface of the semiconductor layer so as to surround the semiconductor region of the first conductivity type; and a conductor with a conductive surface to contact with the semiconductor regions of the first and second conductivity types, wherein the semiconductor layer includes silicon carbide, and wherein at least one of the semiconductor region of the first conductivity type and the conductive surface is not circular on a plan view, and wherein the semiconductor region of the first conductivity type and the conductive surface are shaped such that as the degree of misalignment between the conductive surface and the semiconductor region of the first conductivity type increases from zero through one-third of the width of the conductive surface, a portion of the profile of the conductive surface that crosses the semiconductor region of the first conductivity type has smoothly changing length, thereby decreasing the length of the portion of the profile of the conductive surface that crosses the semiconductor region of the first conductivity type and therefore preventing from decreasing the effective gate width of the transistor.