PURPOSE: To form an ultrafine emitter region of submicron width in an ultrafine base region by forming the holes of base and emitter regions by patterning, and then narrowing the hole side wall of the emitter region by an insulating film.
CONSTITUTION: After a mask type insulating film 3 is formed on an N type epitaxial layer 2 of an Si substrate 1, a hole 9 of a base region is formed. Then, a P+ type polysilicon 20 to become a base electrode is formed on the overall surface, an SiO2 film 11 is formed. A hole 12 is formed inside from the hole 9 at the film 11, and the polysilicon 10 of the hole 12 is removed by a dry etching method having good directivity. In case of oxidizing then, P type impurity is diffused from the polysilicon 10 to form a region 4 to compensate the base. Further, the film 11 on the bottom of the groove is removed by selective etching method, and a hole 13 of an emitter region is formed. P type impurity is implanted through the hole 13 to form a true base region 5. Further, N type impurity is implanted through the hole 13 to form an emitter electrode 14.
KUSUDA YUKIHISA
TAGAMI TAKASHI
Next Patent: TRANSISTOR