US Patent 7282764 Semiconductor device

A semiconductor device having high ruggedness is provided. The distance Wm2 between buried regions, positioned at the bottoms of different base diffusion regions and face each other, is set smaller than the distance Wm1 between buried regions positioned at the bottom of the same base diffusion region (Wm1>Wm2). An avalanche breakdown occurs under the bottom of the base diffusion region, and the avalanche current is not passed through a high resistance part immediately under the source diffusion region in the base diffusion region, thereby providing high withstand strength against destruction.