electrically programmable read only memory device
An electrically programmable read only memory device accumulates electrons in a floating gate electrode so as to change the threshold level at a first control gate electrode capacitively coupled with the floating gate electrode, and a second control gate electrode is further capacitively coupled with the floating gate electrode through a composite gate insulating film structure implemented by a silicon nitride film sandwiched between silicon oxide films, when the electrons are evacuated from the floating gate electrode in ultra-violet radiation, the second control gate electrode is biased to a certain voltage level lower than a virgin threshold level provided upon completion of a fabricating process so that the threshold level is lowered rather than the virgin threshold level for speed up of a read-out operation.