| 摘要 |
There is provided a method of fabricating a semiconductor device, including the steps of, in consequence, (a) partially forming a buried layer in a semiconductor substrate and also forming an epitaxial layer on the buried layer, (b) forming a collector region in the epitaxial layer by selectively introducing impurities into the epitaxial layer so that the collector region reaches the buried layer, (c) forming an insulating film on the epitaxial layer, (d) forming a polysilicon film on the insulating film, (e) patterning the polysilicon film to form a base electrode, (f) forming an interlayer insulating film over the base electrode and the insulating film, (g) patterning both the interlayer insulating film and the base electrode to form a base opening at a region at which a base region is to be formed and a collector opening above the collector region, (h) side-etching portions of the insulating film located below the base electrode to form undercut hollow portions in the insulating film, (i) filling the undercut hollow portions with polysilicon, (j) forming a base region in the epitaxial layer by introducing impurities into the epitaxial layer through the base opening, (k) forming sidewalls on inner walls of the base collector openings, (l) forming an impurities doped polysilicon film over a resultant, and (m) patterning the polysilicon film to form an emitter electrode and the collector electrode. The method makes it possible decrease the number of photolithography steps by two relative to a conventional method.
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