Patent ID: 8711535

Claim:
An ESD protection device, comprising: a substrate, having a first conductive type; a first well, having a second conductive type and disposed in the substrate, and the first well being electrically connected to a first switching device; a first doped region, having the first conductive type and disposed in the first well, and the first doped region and the first well being electrically connected to a first power rail; a second doped region, having the second conductive type and disposed in the substrate, and the second doped region and the substrate being electrically connected to a second power rail; a third doped region, having the second conductive type and disposed in the first well between the first doped region and the second doped region, and the first well being electrically connected to the first switching device by the third doped region, wherein the third doped region partially surrounds the first doped region; and a fourth doped region, having the second conductive type and disposed in the first well, and the first doped region being disposed between the fourth doped region and the second doped region, wherein the fourth doped region electrically connects the first well and the first power rail, the first well and the fourth doped region constitutes a first resistor, and the third doped region doesn't extend to be disposed between the first doped region and the fourth doped region in an arranged direction of the first doped region and the fourth doped region; wherein when an ESD event does not occur, the first switching device is turned on, and a potential of the first well is larger than or equal to a potential of the first doped region; and when the ESD event occurs, the first switching device is turned off, and the potential of the first well is smaller than the potential of the first doped region.