In this paper for the first time, a novel partial SOI LDMOS with variable drift region doping concentration (VDRDC-PSOI) has been proposed. The introduced doping regions in the partial buried oxide enhance peaks of the electric field to achieve maximum breakdown voltage. We demonstrate that the electric field is modified by producing two additional peaks of electric field. These peaks decrease the common peaks near the drain and gate junctions. Hence, a more uniform electric field is obtained. The two-dimensional numerical analysis is performed to investigate the breakdown characteristics of VDRDC-PSOI structure. 2-D numerical simulation results show that breakdown voltage (BV) for proposed structure is increased by 127% in comparison with C-PSOI structure. The PSOI devices with variable doping region concentration overcome the disadvantages of the conventional PSOI (C-PSOI) devices and are shown to keep better balance between the self-heating effects (SHE) and the breakdown voltage which can be optimized at the same time. Simulations results show that the maximum temperatures of the VDRDC-PSOI and C-PSOI structures are 441 and 500?K at VDS = 40 V. The substrate temperature and gate-source voltage are chosen 300?K and 10 V, respectively. Furthermore, the drive current is improved. The current of the VDRDC-PSOI and C-PSOI structures are 108 μA and 88 μA, respectively for a drain-source voltage VDS = 20V.