A semiconductor structure is provided. A substrate has a first conductivity type. A first well and a second well are formed in the substrate. The first well has a second conductivity type. The second well has the first conductivity type. A doped region is formed in the first well and has the second conductivity type. A gate structure is disposed over the substrate and overlaps a portion of the first well and a portion of the second well. An insulating layer is disposed over the substrate and is spaced apart from the gate structure. A conducting wire is disposed on the insulating layer and includes a first input terminal and a first output terminal. The first input terminal is configured to receive an input voltage. The first output terminal is electrically connected to the doped region.