Ldmos device

A lateral double-diffused MOSFET (LDMOS) device, comprising:

• a semiconductor substrate;
• a drift region and a body region in the semiconductor substrate;
• a first shallow trench isolation structure in the drift region;
• a gate dielectric layer disposed on a side surface and a bottom surface of a first trench, wherein the first trench is positioned having a first portion in the drift region next to the first shallow trench isolation structure and a second portion in the semiconductor substrate between the drift region and the body region, wherein a sidewall surface of the gate dielectric layer is in contact with a surface of a top edge of the body region;
• a gate electrode on the gate dielectric layer, filling up the first trench, and having a top surface above a top surface of the semiconductor substrate;
• a source region in the body region on one side of the gate electrode;
• and
• a drain region in the drift region on another side of the gate electrode.