| 摘要 |
PURPOSE:To stabilize a threshold voltage by mixing an N-channel MOS transistor of an electrically insulated structure in an N-channel MOS transistor of a structure in which a P-type semiconductor substrate and a P-well layer are electrically conducted. CONSTITUTION:An N-channel MOS transistor Tr1 of a section A has a structure in which a P-type semiconductor substrate 1 and a P-well layer 4 are electrically conducted through a P<+> type buried layer 3. On the other hand, an N-channel MOS transistor Tr2 of a section B is composed by burying an N<+> type buried layer 9 in the substrate 1, forming an N-type epitaxial layer 2 thereon, then forming a P-well layer 4 in the layer 2, and then forming source, drain regions 6 in the layer 4. Thus, since the structure in which the substrate 1 and the layer 4 are electrically insulated by the layer 9 is formed in the section B, the layer 4 is not affected by the influence of the potential of the substrate 1. Accordingly, the influence of a back gate voltage to a threshold voltage is eliminated.
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