Patent ID: 7521734

Claim:
A semiconductor device comprising: a first conductivity type first collector region; a first insulator formed on said first collector region and having an opening; a first conductivity type second collector region formed on said first collector region in said opening; a second conductivity type base region formed on said second collector region; a second conductivity type polycrystalline semiconductor extrinsic base region formed on said first insulator; a first conductivity type emitter region formed on said base region in contact with said base region; a first conductivity type polycrystalline emitter region formed on said emitter region; a second insulator formed in contact with said base region so as to cover a side face of said emitter region; and a second conductivity type extrinsic base region having a triangular shape in a cross-sectional view, including a first surface formed on said base region, a second surface in contact with said polycrystalline semiconductor extrinsic base region, and a third inclined surface which contacts the second insulator at a portion of the third inclined surface adjacent to the first surface and the base region and which inclines to be spaced apart from the second insulator as the distance of the third inclined surface from the base region increases, wherein both bottom faces of said emitter region and said second insulator are approximately on the same plane, and wherein a first portion of said second insulator extends under a bottom surface of the polycrystalline emitter region to separate the bottom surface of the polycrystalline emitter region from the base region, wherein a second portion of said second insulator is formed in contact with a side face of said polycrystalline emitter region, and wherein said first and second portions of said second insulator consist of the same material.