Patent ID: 7224022

Claim:
A semiconductor device comprising: a first conductivity type semiconductor substrate; a vertical unit cell that employs the first conductivity type semiconductor substrate as a first conductivity type drain layer; and a separating member formed on the first conductivity type semiconductor substrate, separating the unit cell from other element, the unit cell comprising: a semiconductor structure comprising three semiconductor layers selectively formed on a main surface of the first conductivity type semiconductor substrate, the three semiconductor layers including a second conductivity type semiconductor layer and two first conductivity type semiconductor layers formed to interpose the second conductivity type semiconductor layer from both side surfaces, a pn junction boundary between the second conductivity type semiconductor layer and each of the first conductivity type semiconductor layers being substantially vertical to the main surface of the first conductivity type semiconductor substrate, a second conductivity type base layer formed on an upper surface of the second conductivity type semiconductor layer and having an impurity concentration higher than the second conductivity type semiconductor layer; a first conductivity type source diffusion layer selectively formed on a surface of the second conductivity type base layer; a gate insulating film formed on the second conductivity type base layer interposed between the first conductivity type source diffusion layer and one of the first conductivity type semiconductor layers, and a gate electrode formed on the gate insulating film, wherein a plurality of unit cells identical to the unit cell are formed such as to employ the first conductivity type semiconductor substrate as a common first conductivity type drain layer, and a termination structure is provided in which another first conductivity type and another second conductivity type semiconductor layers are formed on a terminal portion of the first conductivity type semiconductor substrate wherein the termination structure is connected to a unit cell that is closest to the terminal portion via an insulating film formed on the first conductivity type semiconductor substrate.