Patent ID: 8017975

Claim:
A semiconductor device, comprising: a heterojunction bipolar transistor and a heterojunction field effect transistor formed on a same semiconductor substrate, wherein the heterojunction bipolar transistor includes a sub-collector layer, a collector layer, a base layer, and an emitter layer which are sequentially stacked, said sub-collector layer includes an external sub-collector region, and an internal sub-collector region disposed on said external sub-collector region, a mesa-shaped collector part and a collector electrode are separately formed on said external sub-collector region, said collector part including said base layer, said emitter layer, said collector layer, and said internal sub-collector region, the heterojunction field effect transistor includes a cap layer, a source electrode, and a drain electrode, said cap layer including a portion of said external sub-collector region, and said source electrode and said drain electrode being formed on said cap layer, said cap layer is stacked commonly with said external sub-collector region, and has a same thickness as a thickness of said external sub-collector region, said external sub-collector region has a thickness between not less than 50 nm and not more than 300 nm, and said internal sub-collector region has a thickness of not less than 300 nm.