Electrically programmable read only memory having reduced leakage current

Abstract

An electrically programmable read only memory includes a plurality of non-volatile memory elements having control gates which are commonly connected to a first word line and drains which are coupled to a write-down circuit for supplying a write-down voltage to said drains. To prevent the flow of leakage current caused by parasitic capacitance, at least one of source electrodes of the plurality of non-volatile memory elements is connected to ground potential through the drain-source path of a first switch MISFET whose gate electrode is connected to the first word line. When a word line driving signal of non-selection level is applied to the first word line, the first switch MISFET is non-conductive. Thus, leakage current is prohibited from flowing through the first switch MISFET. Further, in order to prevent deterioration of the rewrite-down efficiency of the memory, the write-down circuit includes a pn-junction element having a junction characteristic which is substantially equal to the drain junction characteristic of the non-volatile memory elements. The level of a write-down voltage to be applied to the drains of the non-volatile memory element is determined on the basis of the reverse breakdown voltage of the pn-junction element. Thus, the breakdown of the drain junction of the non-volatile memory elements during a write-down operation can be prevented, so that deterioration of the rewrite-down efficiency of the electrically programmable read only memory can be prevented.