| 摘要 |
PURPOSE:To prevent a semiconductor integrated circuit from causing a parasitic effect such as a latchup by forming a high density impurity layer in the bottom of a device in which a resistance value alters according to an input to reduce a delay time without loss the performance of a protective circuit for the integrated circuit. CONSTITUTION:A low density P-type source, drain regions 407, 408 are formed deeply in contact with a high density N-type region 302. Thus, when the breakdown voltages of the source, drain and the region 302 of an MOSFET are suitably reduced so that a negative large voltage is applied to the source or the drain, a current flows through a junction between the regions 407, 408 and the region 302 to prevent a protective circuit itself from breaking down. Since the thicknesses of the regions 407, 408 are increased, a conductivity between the source and the drain when the MOSFET is conducted is raised.
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