A semiconductor device is disclosed including a semiconductor layer, a first well doped with dopants of a first conductivity type defined in the semiconductor layer, a second well doped with dopants of a second conductivity type different than the first conductivity type defined in the semiconductor layer adjacent the first well to define a PN junction between the first and second wells, and an isolation structure positioned in the second well. The semiconductor device also includes a first source/drain region positioned in the first well, a second source/drain region positioned in the second well adjacent a first side of the isolation structure, a doped region positioned in the second well adjacent a second side of the isolation structure, and a gate structure positioned above the semiconductor layer, wherein the gate structure vertically overlaps a portion of the doped region.