Patent ID: 7345347

Claim:
A semiconductor device comprising: a semiconductor substrate having a first conductivity type; a first element region formed at an element formation surface side of said semiconductor substrate; and a second element region formed at said element formation surface side of said semiconductor substrate; wherein said first element region includes: a first region having said first conductivity type, a second region having a second conductivity type opposite to said first conductivity type, and a third region having said second conductivity type and being formed closer to a bottom side of said semiconductor substrate that is opposite said element formation surface side than said first region is to said bottom side, so as to isolate said first region from said bottom side of said semiconductor substrate; and said third region includes: a second conductivity type first lower region contacting a lower face of said first region, and a second conductivity type second lower region formed closer to the bottom side of said semiconductor substrate than said first lower region and contacting a lower surface of said first lower region, and having an impurity concentration less than said first lower region.