An antifuse circuit includes a capacitor and a detector. The capacitor is formed using standard MOS processes in a well. The gate serves as one electrode and the well serving as another electrode of the capacitor. The antifuse is programmed by externally provided radiation that can rupture the gate oxide so that the gate and well can contact each other. The gate and well form a PN junction, transforming the capacitor into a diode. The diode provides the conductive path of the programmed antifuse.