It is the object of the present invention to provide a semiconductor device having an improved breakdown voltage on high power output, the semiconductor device comprising a n-type GaAs subcollector layer 101, a n-type GaAs intermediate collector layer 102 formed between a collector layer 103 and the subcollector layer 101, the n-type GaAs collector layer 103, a p-type GaAs base layer 104, a n-type InGaP second emitter layer 105, a n-type GaAs first emitter layer 106, and a n-type InGaAs emitter contact layer 107, and a concentration of impurities in the intermediate collector layer 102 is higher than a concentration of impurities in the collector layer 103 and is lower than a concentration of impurities in the subcollector layer 101.