PURPOSE: To reduce the resistance between an base and an emitter by shortening the distance between an emitter region and a graft base region.

CONSTITUTION: A base region 3 is formed in the surface area of a p-type silicon substrate 1, and graft base regions 5 are formed on both sides of it, and an emitter region 6 is formed in the base region 6. The polysilicon film on the graft base region is constituted of a high-concentration base polysilicon film 4a and a low-concentration base polysilicon film 4b. At patterning of these polysilicon films, the low-concentration polysilicon film is high in etching rate, so the polysilicon film 4a is side-etched greatly Ions are implanted into the emitter region, with the photoresist mask used at etching left.