Lateral diffusion metal-oxide semiconductor device

A lateral diffusion metal-oxide semiconductor (LDMOS) device, comprising:

• a first gate structure and a second gate structure extending along a first direction on a substrate;
• a first source region extending along the first direction on one side of the first gate structure, wherein a length of a sidewall of the first source region directly contacting a sidewall of the first gate structure is less than a length of the sidewall of the first gate structure directly contacting the first source region under a top view perspective;
• a second source region extending along the first direction on one side of the second gate structure;
• a drain region extending along the first direction between the first gate structure and the second gate structure, wherein a length of the drain region is greater than the length of the sidewall of the first source region;
• a guard ring surrounding the first gate structure and the second gate structure under a top view perspective, wherein the guard ring directly contacts the first source region and sidewalls of the first gate structure and the second gate structure extending along a second direction but not contacting sidewalls of the first gate structure and the second gate structure extending along the first direction;
• and
• a shallow trench isolation (STI) surrounding the guard ring.