Semiconductor device and fabrication method thereof

A method for forming a lateral diffusion MOS (LDMOS) transistor, comprising:

• providing a substrate having a drift region and an insulation structure, spaced apart in the substrate by a first spacing;
• forming a gate material layer over the substrate;
• performing a first etching process on the gate material layer to remove a first portion of the gate material layer and expose a first portion of the substrate;
• performing a first ion implantation process on the first portion of the substrate to form a body region in the substrate, the body region being doped with first dopant ions and extending to under a remaining portion of the gate material layer, wherein
• the body region surrounds the insulation structure from two sides and a bottom of the insulation structure and exposes the top surface of the insulation structure, and
• a dimension of an overlapping area of the body region to the remaining portion of the gate material layer in a direction parallel to a top surface of the substrate in a cross-section view is less than 0.1 μm;
• performing a second etching process on the remaining portion of the gate material layer to remove a second portion of the gate material layer to form a gate electrode, the second portion of the gate material layer being located on a side away from the body region, the gate electrode covering a portion of the body region, a portion of the drift region, and a portion of the substrate between the drift region and the body region;
• and
• forming a source region in a surface portion of the body region on one side of the gate structure between the insulation structure and the gate electrode, wherein the source region extends under the gate electrode;
• and
• forming a doped region in a surface portion of the body region on the side of the insulation structure away from the gate electrode, wherein the doped region are isolated from the source region by the insulation structure.