Patent ID: 7719031
Filing Date: 2010-05-18
Classification: H01L

Abstract:
1. A bipolar transistor comprising: a substrate; a intrinsic base region having a silicon buffer layer comprised of silicon which is formed on said substrate, and a composition-ratio graded base layer which is formed on the silicon buffer layer and comprises silicon and at least germanium and where a composition ratio of the germanium to the silicon in the composition-ratio graded base layer varies in a thickness direction of the composition-ratio graded base layer; and an extrinsic base region having an extrinsic base formation layer comprised of silicon which is formed on said substrate and adjacent to the silicon buffer layer; wherein a thickness of the extrinsic base formation layer is substantially equal to a thickness of the silicon buffer layer, each of the extrinsic base formation layer and the silicon buffer layer has a thickness of not less than 40 nm, and a surface of the extrinsic base formation layer is silicided.