| 摘要 |
PURPOSE:To prevent a semiconductor device from malfunctioning itself due to injection from input signals by forming an input protective circuit within the area of a semiconductor different in conduction type from a semiconductor substrate constituting a semiconductor device. CONSTITUTION:An input protective circuit is constituted inside an N type well layer 12 formed above a P type silicon substrate 1. In the case that negative surge voltage is applied, a p-channel type MOS transistor 8 constituting the input protective circuit turns into ON condition and electrons injected from a P type diffusion area 9 are immediately released to the earth potential set in a P type diffusion area 10. On the contrary, in the case that positive surge voltage is applied, a diode composed of the P type diffusion area 9 connected to an input signal terminal 2 and the N type well layer 12 turns into the forward direction and releases the positive surge to an external power source (VPP) connected to the N type well layer 12. This way, electrons injected from the input signal terminal 2 never enter the inside of the P type silicon substrate 1, and injection from input signals can be prevented. |
