Antifuse of semiconductor device and method of fabricating the same

An antifuse of a semiconductor device and a method of fabricating the same capable of causing an antifuse to stably operate by rupturing the antifuse at a specific point and stabilizing a current level when rupturing the antifuse are provided. The antifuse may include: a device isolation layer defining a first active region in a semiconductor substrate; a first and second junction regions provided in the first active region; a second active region formed over the first junction region; a gate insulating layer formed over the first active region and the second active region; and a gate electrode formed over the gate insulating layer.