In this paper, a two-stage trigger (TST) scheme is proposed to implement a low-capacitance and zero-ohm input resistance electrostatic-discharge (ESD) protection device for nanometer technology applications. Besides the main trigger device diode string, the output transistor can also be used as the trigger device. The dimension of the main trigger device can be reduced for minimizing its capacitance with the additional trigger device. Moreover, the output transistor can be as the driving device without any series resistor. This is because the diode string can help to prevent integrated circuits (ICs) from ESD damage before the primary ESD protection device turns on.