Patent ID: 8420493

Claim:
A method of forming a semiconductor structure comprising: providing a semiconductor material structure including at least a silicon-germanium alloy layer on a substrate, wherein said silicon-germanium alloy layer has a doping of a first conductivity type; forming an extrinsic base directly on a top surface of a portion of said semiconductor material structure by depositing and patterning a semiconductor material having a doping of said first conductivity type; forming a first trench by removing a first portion of said semiconductor material structure from one side of said extrinsic base and forming a second trench by removing a second portion of said semiconductor material structure from an opposite side of said extrinsic base; and forming an emitter in said first trench and a collector in said second trench by selectively depositing silicon epitaxially, wherein said emitter and said collector have a doping of a second conductivity type that is the opposite of said first conductivity type.