Patent ID: 7880222

Claim:
A semiconductor device, comprising: a support substrate, a first semiconductor element placed on said support substrate; and a second semiconductor element placed on said first semiconductor element, wherein said first semiconductor element comprises a semiconductor base which comprises: a first semiconductor region of a first conductivity type; a second semiconductor region of a second conductivity type formed in a surface region of said first semiconductor region and having a surface area; and a third semiconductor region of the first conductivity type formed in a surface region of said second semiconductor region, said third semiconductor region having a surface area, and said semiconductor base of said first semiconductor element comprises: a first region in which said third semiconductor region occupies said second semiconductor region at a first ratio and which is formed at a center part of said semiconductor base; and a second region in which said third semiconductor region occupies said second semiconductor region at a second ratio higher than the first ratio and which is formed at a circumferential part of said semiconductor base so as to surround said first region, wherein said first ratio and said second ratio, each, is a ratio of said surface area of said third semiconductor region relative to said surface area of said second semiconductor region.