US Patent 7655980 Device for ESD protection circuit

A LDNMOS device for an ESD protection circuit including a P-type substrate and an N-type deep well region is provided. The P-type substrate includes a first area and a second area. The N-type deep well region is in the first and second areas of the P-type substrate. The LDNMOS device further includes a gate electrode disposed on the P-type substrate between the first and second areas, a P-type implanted region disposed in the first area of the P-type substrate, an N-type grade region disposed in the N-type deep well region of the first area, an N-type first doped region disposed in the N-type grade region, a P-type body region disposed in the N-type deep well region of the second area, an N-type second doped region disposed in the P-type body region, and a P-type doped region disposed in the P-type body region and adjacent to the N-type second doped region.