ELECTROSTATIC PROTECTION CIRCUIT FOR SEMICONDUCTOR INTEGRATED CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide an electrostatic protection circuit for a semiconductor integrated circuit which can have both high discharging capacity and a low trigger voltage. SOLUTION: When an electrostatic surge with a positive polarity based upon a ground terminal GND is applied to an input/output pad I/O, a breakdown current Itrig of an n channel MOS transistor NMOS flows from the input/output pad I/O through a p+diffusion layer PD1 and a forward diode of an n-well NW1. Consequently, a thyristor comprising a p+diffusion PD1 as the anode of the diode, the n-well NW1, a p well PW1, and an n+diffusion layer ND2 as the source of a transistor NMOS operates, to discharge the electrostatic surge to the ground terminal GND. COPYRIGHT: (C)2003,JPO