| 摘要 |
PURPOSE:To make it possible to use the device at high breakdown strength, by providing a gate electrode and a gate oxide film on a substrate, connecting one of source/drain regions formed thereon so as to hold an inverted layer region in-between to an input terminal, connecting the other to a grounding terminal or a power source terminal, and connecting either of them to the gate electrode. CONSTITUTION:An N well, which is used as a gate electrode 7, is formed from the surface to the inside of a P-type semiconductor substrate 8. A gate oxide film 9, source/drain regions 6A and 6B comprising polycrystalline silicon and an inverted layer region 5 are formed on the surface of the N well. Thus a MOS transistor is formed. Then, an external wiring 11 is taken out of a contact region 10 and one end of the source/drain region 6B and connected to an input terminal. An external wiring 12 is taken out of one end of the source/drain region 6A and connected to a grounding terminal. When an excessive voltage is applied, the MOS transistor is turned ON, and the voltage is clipped to a threshold voltage value. When the gate oxide film 9 is formed at an appropriate thickness, the device can be operated with the input having the desired breakdown strength with respect to the input signal.
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