Patent ID: 8237241

Claim:
A semiconductor device comprising: a semiconductor layer; an isolation region dividing the semiconductor layer into a plurality of element-formation regions; a semiconductor element formed in a first element-formation region of the element-formation regions; a first diffusion layer formed in the first element-formation region and forming a first PN junction region with the isolation region that defines the first element-formation region; and a second diffusion layer formed in a second element-formation region of the element-formation regions, the first and second element-formation regions being disposed next to each other so as to be divided by the isolation region, and different voltages being applied to the first and second diffusion layers, wherein a junction breakdown voltage of the first PN junction region is lower than a junction breakdown voltage of an element PN junction region included in the semiconductor element, the first and second diffusion layers are each disposed at a bottom portion of the semiconductor layer and each have a lower resistance than the semiconductor layer, and at a time of breakdown, a current path is formed between the first and second diffusion layers through the isolation region.