Abstract: A novel SOI P-LDMOS with field oxide partly on the surface of the drift is proposed.The lack of the field oxide avoids defleg mating the impurity of the driftsurface in the high temperature process.The surface is implanted after the preparation of field oxide and gate oxide.Since there is no subsequent long-time high-tempera ture process,the impurity concentr ation of the surface of the drift is improved.Thus the on-resistance of the device decreases.The simulation results manifest that the on-resistance of the proposed P-LDM OS is reduced by 24.7%,the breakdown voltage is improved by 17.3%and the saturated current is increased by 26.7%,comparing to the conventional P-LDMOS.