A semiconductor structure and a method for forming the same are provided in embodiments of the present disclosure. The forming method includes: providing a base; forming a trench in the base, and forming a first dielectric layer on the bottom surface and side walls of the trench; forming a conductor layer, the conductor layer covering the first dielectric layer on the bottom surface of the trench; forming a second dielectric layer in the trench on the conductor layer; and forming a drift region on a side, provided with the trench, of the base. The forming method can improve the breakdown voltage of an LDMOS device and also reduce the Ron of the LDMOS device, thereby improving the performance of the LDMOS device.