Patent ID: 9640631
Date: 2017-05-02
CPC Classifications: H01L

Claim:
1. A method for forming a bipolar transistor, the method comprising: forming a first doped region at a top surface of a semiconductor substrate; forming a first semiconductor layer over the top surface of the semiconductor substrate, wherein the first semiconductor layer includes a side surface that is substantially perpendicular to the top surface of the semiconductor substrate; forming a first insulating layer between the first doped region and the first semiconductor layer; forming a stack that includes a second semiconductor layer and a second insulating layer over the first semiconductor layer, wherein the second semiconductor layer includes a side surface that is substantially perpendicular to the top surface of the semiconductor substrate; forming an opening through said stack, said first semiconductor layer, and the first insulating layer above the first doped region; forming a single-crystal silicon region in said opening; forming a silicon-germanium region at a surface of the single-crystal silicon region and in contact with the side surfaces of the first semiconductor layer and of the second semiconductor layer; and forming a second doped region in the opening and over the single-crystal silicon region.