PURPOSE: To decrease base resistance by a method wherein self-alignment is done between a base junction layer and an emitter layer and diffusion from a base junction layer is effected with precision.
CONSTITUTION: A P type base 12 is diffused into an N epitaxial layer 11 to act as collector on an N+ type Si substrate 10 and a pattern of BSG14 is formed, on which an undoped silica glass 15 and Si3N4 16 are placed in piles. Edges E the BSG14 are subjected to photoetching of a coarse accuracy of ±Δ, and a P layer 12 is exposed. B ions are then implanted, using a photoresist 17 and films 18 and 19 as mask. The photoresist 17 is removed, and then, a base junction layer 21, a B ions implanted P layer 22a and a high resistance P base layer 22b are created by heat treatment and oxidation. Next, Si3N4 18 is removed, a photoresist mask 23 is applied, P ions are implanted, and an N emitter 24 is provided. Then metal leads 25 and 26 are bonded after removal of remaining Si 19. The gap between the base junction layer 21 and the N emitter layer 24 is virtually shortened thanks to the P layer 22a. The base resistance is reduced and a bipolar transistor suitable for radio frequency use is completed.
EZAKI TAKEYA
ISHIKAWA OSAMU
KAJIWARA KOSEI
