The present invention provides a semiconductor device including a substrate, a deep well, a high-voltage well, and a doped region. The substrate and the high-voltage well have a first conductive type, and the deep well and the doped region have a second conductive type different from the first conductive type. The substrate has a high-voltage region and a low-voltage region, and the deep well is disposed in the substrate in the high-voltage region. The high-voltage well is disposed in the substrate between the high-voltage region and the low-voltage region, and the doped region is disposed in the high-voltage well. The doped region and the high-voltage well are electrically connected to a ground.