| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a semiconductor integrated circuit of high level of integration at a low cast by restraining interference of noise between an analog part and a digital part, in a semiconductor integrated circuit in which digital circuits and analog circuits are mixedly mounted on a chip. SOLUTION: This digital/analog mixed mount semiconductor integrated circuit has a second semiconductor layer 4 on a semiconductor substrate 3 of low resistance which layer has higher resistivity and the same conductivity type as the substrate, and a well region on the second semiconductor layer 4 which region is composed of N-wells 5-1, 5-2 connected with a power source and P-wells 6-1, 6-2 connected with ground. In at least a part of the side surface and the bottom surface of the well region, third semiconductor regions 11-1, 11-2 are formed which have resistivity higher than that of the layer 4 and the same conductivity type as that of the layer 4.
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