Patent ID: 6927118

Claim:
A method for fabricating a semiconductor device which is formed on a semiconductor substrate and which operates as a bipolar transistor provided with an emitter, a base, and a collector, said method comprising: a step (a) of forming said collector of a first conductivity type at a portion of a surface of said semiconductor substrate, a step (b) of forming a first insulating layer on said semiconductor substrate and subsequently forming, in a portion of said first insulating layer situated above said collector, a collector opening portion reaching said collector, a step (c) of epitaxially growing, on said semiconductor substrate, a semiconductor layer including at least a layer of a second conductivity type constituting said base, a step (d) of forming, on said semiconductor substrate, an etching stopper layer which serves as an etching stopper against dry etching and which has insulating ability and a masking layer against wet etching in such a way that said masking layer overlies said etching stopper layer, a step (e) of exposing a part of said etching stopper layer by removing a part of said masking layer by means of dry etching, a step (f) of forming a base junction opening portion reaching said semiconductor layer by subjecting said part of said etching stopper layer exposed by means of said dry etching of said step (e) to a wet etching treatment using the remaining part of said masking layer as a mask, a step (g) of layering, on said semiconductor substrate, a first conductor layer and a second insulating layer and subsequently forming a base opening portion reaching said etching stopper layer by carrying out a dry etching treatment so that said masking layer, said first conductor layer, and said second insulating layer are penetrated locally, a step (h) of forming a third insulating layer covering a side surface exposed to said base opening portion, a step (i) of exposing said semiconductor layer at the bottom of said base opening portion by removing a portion of said etching stopper layer exposed to said base opening portion by means of a wet etching treatment, and a step (j) of forming said emitter by filling up said base opening portion.