Lateral double diffused metal-oxide-semiconductor device and method for fabricating the same

A method for fabricating a lateral double diffused metal oxide semiconductor (LDMOS) device, comprising:

• performing a semiconductor substrate, having a first conductivity type;
• forming a first doped region in a portion of the semiconductor substrate, having the first conductivity type;
• forming an epitaxial semiconductor layer over the semiconductor substrate, having the first conductivity type, wherein during formation of the epitaxial semiconductor layer, the first doped region extends upward and a diffused region is formed in a portion of the epitaxial semiconductor layer;
• forming a gate structure over a portion of the epitaxial semiconductor layer;
• forming a second doped region in a portion of the epitaxial semiconductor layer adjacent to a first side of the gate structure, having the first conductivity type;
• forming a third doped region in a portion of the epitaxial semiconductor layer at a second side of the gate structure opposite to the first side, having a second conductivity type opposite to the first conductivity type;
• forming a fourth doped region in a portion of the second doped region, having the second conductivity type;
• forming a fifth doped region in a portion of the third doped region, having the second conductivity type;
• forming an insulating layer over the third doped region, the gate structure, and a portion of the fourth doped region;
• forming a trench in a portion of epitaxial semiconductor layer underlying the third doped region, the second doped region, and partially exposing the diffused region;
• performing an ion implant process, implanting dopants of the first conductivity type into the diffused region exposed by the trench;
• conformably forming a conductive layer in a bottom surface and a plurality of sidewalls of the trench, covering the insulating layer, wherein the conductive layer physically contacts the diffused region;
• and
• forming a dielectric layer in the trench and over the conductive layer, wherein the diffused region physically contacts the semiconductor substrate and surrounding portions of the sidewalls and bottom surface of the trench.