Patent ID: 7755143

Claim:
A semiconductor device, comprising: a substrate having a protected device area, a guard ring area and a periphery device area, wherein the substrate has a conductive first type; a protected device in the protected device area; an electrostatic discharge power clamp device comprising an outer first guard ring and an inner second guard ring in the guard ring area enclosing the protected device, wherein the first guard ring comprises: a first well region having the first conductive type; and a first doped region having the first conductive type and a second doped region having a second conductive type in the first well region, adjacent to a surface of the substrate; the second guard ring comprises: a second well region having the second conductive type; and a third doped region having the second conductive type in the second well region, adjacent to the surface of the substrate; and an input/output device in the periphery device area, coupled to the electrostatic discharge power clamp device.