A vertical double-diffused metal oxide semiconductor (VDMOS) with double P-well structure was proposed based on the theory of field limiting ring termination technology. The relations of the breakdown voltage with the parameters of the P-well and doping concentration of the drift region was simulated by numerical simulation software. The surface electric field was extracted when the device was struck and the breakdown principle was analyzed. The results show that the breakdown voltage increases with the increase of number and junction depth of the P-well when the doping concentration of the drift region is constant. When the parameters of the P-well are constant, the breakdown voltage increases first and then decreases with the increase of doping concentration of the drift region. After the device parameters were optimized, the effective length of the termination was only 26 μm and the breakdown voltage (VB) of the device can reach 3200 V, a 305% improvement over conventional planar gate VDMOS. And the distribution of the surface electric field was relatively uniform and the maximum value of surface electric field was 1.21×106 V/cm. Therefore, the stability and reliability of the termination could be greatly enhanced.
