Patent ID: 7671447

Claim:
A semiconductor device with a semiconductor body comprising a bipolar transistor having an emitter region, a base region and a collector region of, respectively, a first conductivity type, a second conductivity type opposite to the first conductivity type, and the first conductivity type, wherein, viewed in projection, the emitter region is surrounded by the base region, and the collector region laterally borders the base region, wherein the base region contains a highly doped sub-region, wherein a doping concentration of the highly doped sub-region has a delta-shaped profile in a thickness direction, and said highly doped sub-region extends laterally to border the collector region, wherein the collector region is not located entirely below the base region, wherein the base region further comprises a first semiconductor layer attached on the highly doped sub-region and a second semiconductor layer attached on the first semiconductor layer, and wherein the first semiconductor layer contains an SiGe mixed crystal and the second semiconductor layer contains silicon.