In one embodiment, the semiconductor device includes a first source of a first doping type disposed in a substrate. A first drain of the first doping type is disposed in the substrate. A first gate region is disposed between the first source and the first drain. A first channel region of a second doping type is disposed under the first gate region. The second doping type is opposite to the first doping type. A first extension region of the first doping type is disposed between the first gate and the first drain. The first extension region is part of a first fin disposed in or over the substrate. A first isolation region is disposed between the first extension region and the first drain. A first well region of the first doping type is disposed under the first isolation region. The first well region electrically couples the first extension region with the first drain.