Heterojunction bipolar transistor

Abstract

A method for forming a heterojunction bipolar transistor including the steps of: forming in a semiconductor substrate a collector area of a first doping type; growing by epitaxy above a portion of the collector area a silicon/germanium layer of a second doping type forming a base area; forming above the silicon/germanium layer a sacrificial emitter formed of a material selectively etchable with respect to the silicon/germanium layer and with respect to the layers and consecutively-formed insulating spacers; forming first insulating spacers on the sides of the sacrificial emitter; growing by epitaxy a silicon layer above the exposed portions of the silicon/germanium layer; forming second insulating spacers adjacent to the first spacers and laid on the silicon layer; covering the entire structure with an insulating layer; partially removing the insulating layer above the sacrificial emitter and removing the sacrificial emitter; filling the space previously taken up by the sacrificial emitter with a semiconductor material of the first doping type.

Dependencies are inferred from the claim text.