Semiconductor devices and methods of forming the same are provided. The semiconductor device may include a semiconductor element disposed on a substrate and including an insulating layer and a gate electrode, a doped region having a first conductivity-type on the substrate, a conductive interconnection electrically connected to the gate electrode, and a first contact plug having a second conductivity-type and electrically connecting the conductive interconnection and the doped region to each other and constituting a Zener diode by junction with the doped region.