In recent years, with the development of automotive electronics and power drives, LDMOS with higher integration has received attention as a popular power device. How to increase its breakdown voltage and reduce its specific on-resistance has become the key to improve the device’s performance. Based on SOI LDMOS technology, a novel structure with a vertical field plate introduced in the SiO2 trench surrounded by a 4 μm high-K dielectric film was proposed in this paper. Compared with the traditional trench LDMOS, the vertical field plate and the high-K dielectric film fully guide the potential lines into the trench, which improves the breakdown voltage. In addition, the metal-insulator-semiconductor capacitive structure formed by the vertical field plate, the high-K dielectric and the drift region can increase the amount of charge on the surface of the drift region and reduce the specific on-resistance. Through 2-D simulation software, by introducing a vertical field plate with a width of 0.3 μm and a depth of 6.8 μm into a depth of 7.5 μm trench, an LDMOS was realized, with the breakdown voltage of 300 V, the specific on-resistance of 4.26 mΩ·cm2, and the Baliga quality factor of 21.14 MW·cm-2.