Semiconductor device capable of preventing reduction of cut-off frequency by Kark effect even when operated within a high electric current density range

摘要

In a semiconductor device which includes a semiconductor substrate, a collector region of a first conductivity type formed on the semiconductor substrate, a base region of a second conductivity type reverse to the first conductivity type, an emitter region of the first conductivity type formed within the base region, an intermediate semiconductor layer of the second conductivity type is formed within the collector region, an additional semiconductor layer of the first conductivity type is superposed on the intermediate semiconductor layer, and the base region is overlaid on the additional semiconductor layer.