| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of crosstalks in a semiconductor device where an analog and digital mixed integrated circuit is formed. SOLUTION: A p-type epitaxial film 102 is made on the surface of an n-type silicon substrate 101. A digital integrated circuit, in the region 103 of this epitaxial film 102, and an analog integrated circuit region, in the region 104, are made. A great part of the noise introduced from a gate electrode 107 is propagated to the region 104 through the substrate 101 from the region 103 of the epitaxial film 102 and reaches an n" diffused region 109, by completely separating these regions 103 and 104 with a trench structure of element isolating region 105. Here, a depletion layer is made at the interface (that is, the P-N junction face) between the n-type silicon substrate 101 and a p-type epitaxial film 102, so the parasitic capacity C8 and C9 in the vicinity of this interface becomes very small, therefore, the composite capacity of the noise propagation passage at large becomes small. Consequently, this semiconductor device can suppress the propagation of the noise and suppress the occurrence of crosstalk.
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