Patent ID: 7282764

Claim:
A semiconductor device comprising: a resistance layer of a first conductivity type; a plurality of base diffusion regions of a second conductivity type formed in the vicinity of inner surface of the resistance layer and positioned apart from one another; a source diffusion region of the first conductivity type formed in the vicinity of inner surface of each of the base diffusion regions, the source diffusion region being positioned in a region more on the inner side than the edge of each of the base diffusion regions, and the source diffusion region has a depth shallower than that of each of the base diffusion regions; a channel region positioned near the edge of each of the base diffusion regions and between the edges of each of the base diffusion regions and the edges of each of the source diffusion regions; a gate insulating film positioned at least on each of the channel regions; a gate electrode film positioned on the gate insulating film; and a plurality of buried regions of the second conductivity type provided plurally on the bottom of each of the base diffusion regions and connected to each of the base diffusion regions, wherein among pairs of adjacent base diffusion regions, between a center of width direction of one base diffusion region and the center of width direction of the other base diffusion region and in a range deeper than the depth of the base diffusion regions and shallower than the bottom of the buried regions, an amount of impurity of the first conductivity type and an amount of the impurity of the second conductivity type are substantially equal; a PN junction between the buried region and the resistance layer is set such that the avalanche breakdown does not occur at a voltage at which inside of the buried regions is filled with a depletion layer, and a width Wm 1 of the resistance layer in the part between the buried regions adjacent at the bottom of the same base diffusion region is larger than a width Wm 2 of the resistance layer in the part between the buried regions adjacent at the bottoms of the different base diffusion regions.