Patent ID: 7910985

Claim:
A semiconductor device including a semiconductor substrate, a first insulating film formed in the semiconductor substrate and having a rectangular ring form, a MISFET formed within a region of the semiconductor substrate surrounded by the first insulating film, a well region of a first conductivity type formed in the semiconductor substrate and arranged below the first insulating film and along the rectangular ring form, the MISFET comprising: a semiconductor layer of a second conductivity type opposite to the first conductivity type formed in the semiconductor substrate, which serves as a drain region; a base region of the first conductivity type formed in the semiconductor substrate such that the base region is formed in the semiconductor substrate, in which a channel is to be formed; a source region of the second conductivity type formed in the semiconductor substrate such that the source region is formed over the base region, which has a pair of side surfaces opposite each other and an upper surface; a trench formed in the semiconductor substrate, which has contacts with the semiconductor layer, the base region and the source region; a gate insulating film formed inside the trench; a gate electrode formed over the gate insulating film and inside the trench; a second insulating film formed over the gate electrode and the upper surface of the source region; a contact hole formed in the second insulating film and the semiconductor substrate, whose bottom is located lower than the upper surface of the source region, the contact hole having contacts with the source region and the base region; and a source wiring formed in the contact hole electrically connected with the source region and the base region, wherein the source wiring has contacts with the upper surface of the source region and the side surface of the source region, and wherein the trench and the gate electrode extend in the well region such that a termination portion of the gate electrode extends over the first insulating film to extend a depletion layer below the first insulating film.