Semiconductor device including bipolar transistor with improved current concentration characteristics

摘要

An N-type buried region formed in the surface area of a semiconductor substrate is electrically connected to an N-type collector region formed in an epitaxial silicon layer on the semiconductor substrate. A P-type buried region is formed to overlap part of the N-type buried region. The P-type buried region is thick in the upward and downward directions of the N-type buried region. One end portion of the P-type buried region is electrically connected to a P-type base region and the other end portion thereof is electrically connected to a base region formed in the surface area of the semiconductor layer. The base region is applied with a base potential from the base region via the buried region. An N-type emitter region is formed in the base region. The N-type buried region and the P-type buried region are simultaneously formed by use of a difference between the diffusion coefficients of impurity.