A semiconductor device is described. The semiconductor device comprises a protected device in a protected device area of a substrate. An electrostatic discharge power clamp device comprising an outer first guard ring and an inner second guard ring is in a guard ring area of the substrate, enclosing the protected device. The first guard ring comprises a first well region having a first conductive type. A first doped region having the first conductive type and a second doped region having a second conductive type are in the first well region. The second guard ring comprises a second well region having a second conductive type. A third doped region has the second conductive type in the second well region. An input/output device is in a periphery device area, coupled to the electrostatic discharge power clamp device.