Bidirectional ESD diode structure

A bi-directional ESD diode protects a circuit against electrostatic discharge (ESD). The bi-directional diode has a first device and a second device, each including a first region and a third region formed by doping a semiconductor substrate so that it has a P-type conductivity; and a second region and a fourth region formed by doping the semiconductor substrate so that it has an N-type conductivity. The first region of the first device and the fourth region of the second device are for connection to an anode terminal of the bi-directional diode. The fourth region of the first device and the first region of the second device are for connection a cathode terminal of the bi-directional diode. The anode terminal is for connection to a signal terminal of the circuit when the cathode terminal is connected to a positive power line of the circuit, and the cathode terminal is for connection to the signal terminal when the anode terminal is connected to a ground line or a negative power line of the circuit.