| 摘要 |
PURPOSE:To be able to shorten a distance between elements by reducing the depth of an isolation diffusion without providing a buried region by raising the concentration of a substrate to set a specific resistance to 10OMEGA.cm or lower. CONSTITUTION:A P-type silicon substrate 1 uses a high concentration (small specific resistance) with normal bipolar IC. An N-type epitaxial layer 2 is so formed that a P-type isolation region 3 due to the diffusion from further above becomes deeper than the upper end 53 of a buried region 4. In this case, the diffusion depth of the region 3 is so formed deeper than the upper end 52 of the up region 11 due to upward diffusion of the substrate 1 as to separate the layer 2. Since the region 11 is thick due to the high concentration of the substrate 1, the diffusion depth of the region 3 can be formed to be shallower than the surface 51 of the substrate 1. Thus, the lateral diffusion is reduced, and the substantial area of the isolation region can be reduced, thereby reducing a chip size and improving the breakdown strength.
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