Patent ID: 8004041

Claim:
A semiconductor device for surge protection, comprising: a semiconductor substrate; first and second electrodes that are formed respectively on both main surfaces of the semiconductor substrate; and an insulating film that is formed so as to cover a portion of the semiconductor substrate, wherein the semiconductor substrate comprises: a high concentration first conductivity type semiconductor substrate; a low concentration first conductivity type semiconductor layer that is formed on the high concentration first conductivity type semiconductor substrate; a high concentration first conductivity type semiconductor layer that extends from a surface of and into the low concentration first conductivity type semiconductor layer; a second conductivity type semiconductor layer that extends from a bottom surface of the high concentration first conductivity type semiconductor layer into the low concentration first conductivity type semiconductor layer so as to share an axis with the high concentration first conductivity type semiconductor layer; and a cylindrical low concentration second conductivity type semiconductor layer that extends from the surface of the low concentration first conductivity type semiconductor layer into the low concentration first conductivity type semiconductor layer so as to share an axis with the high concentration first conductivity type semiconductor layer, and has an interface with the high concentration first conductivity type semiconductor layer and an interface with the second conductivity type semiconductor layer, the insulating film is formed so as to cover the surface of the low concentration first conductivity type semiconductor layer, a surface of the low concentration second conductivity type semiconductor layer, and a portion of a surface of the high concentration first conductivity type semiconductor layer other than a surface center region, the first electrode is formed so as to span the surface center region of the high concentration first conductivity type semiconductor layer, which is not covered with the insulating film, and a portion of the insulating film, the second electrode is formed so as to cover a surface of the high concentration first conductivity type semiconductor substrate, and the low concentration second conductivity type semiconductor layer has an impurity concentration lower than an impurity concentration of the second conductivity type semiconductor layer.