Power-rail ESD protection circuit with ultra low gate leakage

An ESD protection circuit including a clamping module and a detecting module is provided. The clamping module is coupled between a positive power line and a negative power line. The detecting module includes a triggering unit, a resistor, and a MOS capacitor. An output terminal of the triggering unit is used for triggering the clamping module. The resistor is coupled between the negative power line and an input terminal of the triggering unit. The MOS capacitor is coupled between the positive power line and an input terminal of the triggering unit for ESD protection. During a normal power operation, a switching terminal of the triggering unit enables the MOS capacitor to be coupled between the negative power line and an input terminal of the triggering unit. Thereby, the gate tunneling leakage is eliminated and the problem of mistriggering is prevented.