LDMOS device and manufacturing method thereof

The invention provides an LDMOS (Laterally Diffused Metal Oxide Semiconductor) device and a manufacturing method thereof, the device comprises a substrate, a drift region, a well region, a plurality of shallow trench isolation structures, a source region, a drain region, a body contact region, a grid electrode and a plurality of field plate layers, the shallow trench isolation structures are located in the drift region, the shallow trench isolation structures are in an inverted multi-step shape, and the farther the shallow trench isolation structures are from the well region, the farther the shallow trench isolation structures are from. The more the downward steps of the shallow trench isolation structure are, the farther the shallow trench isolation structure is away from the well region, and the larger the transverse size of the shallow trench isolation structure is. According to the invention, the shallow trench isolation structure is designed to be in an inverted multi-step shape, the number of downward s