An electrostatic discharge (ESD) protection structure comprising a polysilicon gate on an insulating layer on a substrate, said gate having first and second sides, a first heavily doped P-region in the substrate on the first side of the gate, a first heavily doped N-region in the substrate on the second side of the gate, and a shallow trench isolation isolating said first P-region and said first N-region from other structures in the substrate. In a first embodiment, the heavily doped regions are formed in a well having opposite conductivity to that of the substrate and a diode is formed at a PN junction between one of the heavily doped regions and the well. To minimize capacitance between the well and the substrate, the substrate is doped at a level of native doping and the well is isolated so that no other wells or heavily-doped regions are nearby in the substrate. Doping levels in the well and the dimensions of the gate are controlled to minimize on resistance (Ron) of the diode. In a second embodiment, no well is used.