Patent ID: 6563147
Filing Date: 2003-05-13
Classification: H01L

Abstract:
A bipolar transistor comprising:a first-type silicon layer formed on the surface of a silicon substrate so as to contain impurities of first conductivity type; a first-type silicon epitaxial layer formed directly on the first-type silicon layer so as to contain impurities of first conductivity type; a second-type SiGe epitaxial layer which contains impurities of second conductivity type at a first concentration and is formed directly on the first-type silicon epitaxial layer so as to contain germanium at a predetermined concentration profile, and a second-type silicon epitaxial layer formed directly on the second-type SiGe epitaxial layer so as to contain impurities of second conductivity type at a second concentration lower than the first concentration, wherein the germanium content in the second-type SiGe epitaxial layer becomes higher in the vicinity of a boundary region between the second-type SiGe epitaxial layer and the first-type silicon epitaxial layer than in a boundary region between the second-type SiGe epitaxial layer and the second-type silicon epitaxial layer.