In this paper, two 2-D analytical models for the surface potential and electrical field distribution along the drift region of the bulk-silicon RESURF lateral-extended drain MOS (LEDMOS) have been presented, which can be applied in the off- and on-states. The models give an approximate but explicit influence on surface potential and electrical field distributions in terms of the structure and fabricated process parameters, such as the length of the poly gate-field-plate, the implanted dose of the drift region, the diffusion time of the drift region and the substrate doping concentration etc. An effectual way to gain the optimum high-voltage device is also proposed. The analytical results are well supported by the simulation results obtained by Medici. (C) 2003 Elsevier Ltd. All rights reserved.