Method of forming bifets by forming isolation regions connected by diffusion in semiconductor substrate and epitaxial layer

摘要

The present invention relates to a method of manufacturing a semiconductor integrated circuit device, especially a Bi-MOS IC. It comprises: 1. introducing an impurity of a first conductivity type into a plurality of parts of one major surface of a substrate containing a first conductivity type impurity, to form a plurality of impurity-doped regions which have an impurity density higher than that of said substrate; 2. forming an epitaxial semiconductor layer containing an impurity of a second conductivity type on the one major surface of said substrate; 3. introducing a first conductivity type impurity simultaneously into those parts of a major surface of said epitaxial semiconductor layer which overlie said plurality of impurity doped regions; and 4. introducing the first conductivity type impurity of said plurality of impurity-doped regions into said epitaxial semiconductor layer by drive-in diffusion, and subjecting to drive-in diffusion the first conductivity type impurity introduced in the major surface of said epitaxial semiconductor layer, to connect diffused layers formed by the respective diffusions and to form an isolation region and a semiconductor region for forming a MOS FET. MOS FETs can be formed in the semiconductor regions and bipolar transistors in a part of the epitaxial semiconductor layer.