Patent ID: 6847062

Claim:
A semiconductor device comprising: a Si layer functioning as a collector layer and a semiconductor layer formed over the Si layer and functioning as an emitter layer and as a base layer, wherein the semiconductor layer includes: a core base layer whose composition is expressed by Si 1 -x 1 -y 1 Gex 1 Cy 1 (wherein 0<x 1 <1, 0.003≦y 1 <1),and a direct-on cap layer which is formed on and in contact with the core base layer and whose composition is expressed by Si 1 -x 2 -y 2 Gex 2 Cy 2 (wherein 0<x 2 <1, 0≦y 2 <y 1 ), said emitter layer formed in said direct-on cap layer.