A semiconductor device includes a substrate and a device. The substrate has a first surface and a second surface opposite to each other. The substrate includes a first well region, and the first well region includes a first shallow implantation region adjacent to the first surface and a first deep implantation region adjacent to the second surface, in which a dopant concentration of the first deep implantation region at the second surface is substantially equal to 0. The device is disposed on the first surface of the substrate and adjoins the first shallow implantation region.