Patent ID: 6674150
Filing Date: 2004-01-06
Classification: H01L

Abstract:
A heterojunction bipolar transistor comprising a first semiconductor layer made from semiconductor material containing Si as a component; a second semiconductor layer made from semiconductor material containing Si, Ge and C as components, having a band gap narrower than the first semiconductor layer and consisting of a top layer, a center layer and a bottom layer, the center layer having a different composition of Ge or C or a different concentration of impurities as the top or the bottom layer; a third semiconductor layer made from Si as a component, and having a band gap wider than the second semiconductor layer stacked in this order onto a substrate; and a heterojunction barrier provided between the first semiconductor layer and the second semiconductor layer,said heterojunction bipolar transistor further comprising: a collector layer formed in the first semiconductor layer and containing a first conductive impurity; a base layer formed in the second semiconductor layer and containing a second conductive impurity; and an emitter layer formed in the third semiconductor layer and containing a first conductive impurity.