Manufacturing of a graft-base transistor is characterized by: first, forming a layer (8) of oxide of silicon with opening on an n-semiconductor layer (2), at a part to become a base region (3, 4, 3) (FIG. 2a)); then, forming a polycrystalline silicon layer (9) and an overriding silicon nitride layer (10) with an opening (11) thereon (FIG. 2(b)); selectively diffusing P or As to form an n-emitter region (5) (FIG. 2(c)); forming a second silicon oxide layers (12, 13) only on the emitter region (5) and on peripheral regions thereabout, and removing the polycrystalline layer (9) and the silicon nitride layer (10), (FIG. 2(d)) (FIG. 2(e)); and implanting B.sup.+ ions, thereby to form deeper and higher concentration base contact regions (3, 3) and shallower and lower concentration active base region (4).