On-chip electrostatic discharge (ESD) protection structures are frequently used in microchips to protect the core circuit again ESD damages. Relatively large parasitic capacitances associated with these structures, however, can degrade the performance of microchips. In this paper, a new type of supply clamp is studied for the purpose of reducing the parasitic capacitance in ESD protection structures. The approach and physics of the new supply clamp are discussed, and both experimental data and device simulation are provided in support of the investigation. (C) 2003 Elsevier Science Ltd. All rights reserved.