PURPOSE: To provide the title semiconductor device and manufacturing method thereof having excellent characteristics capable of lessening the base resistance furthermore not deteriorating the characteristics at all due to the carrier diffusion from a base to an emitter.

CONSTITUTION: After the formation of a high concentration p type impurity doping region on a part of an n type GaAs collector layer 3, a p type AlGaAs base layer 7, an n type AlGaAs emitter layer 8 are regrown; a high concentration impurity region is formed on a part of the p type AlGaAs base layer 7 by dopant diffusion from the high concentration p type impurity doping region; a base electrode 12 is formed on the impurity region 9; and an emitter electrode 13 is formed on the n type AlGaAs emitter layer 8 on the intrinsic base region.