A semiconductor structure is proposed. A third well is formed between a first well and a second well. A first doped region and a second doped region are formed in a surface of the third well. A third doped region is formed between the first doped region and the second doped region. A fourth doped region is formed in a surface of the first well. A fifth doped region is formed in a surface of the second well. A first base region and a second base region are respectively formed in surfaces of the first well and the second well. A first Schottky barrier is overlaid on a part of the first base region and the first doped region. A second Schottky barrier is overlaid on a part of the second base region and the second doped region.