NEW POLYSILICON-OXIDE-NITRIDE-OXIDE-SILICON ELECTRICALLY ERASABLE PROGRAMMABLE READ-ONLY MEMORY DEVICE APPROACH FOR ELIMINATING OFF-CELL LEAKAGE CURRENT

A new polysilicon-oxide-nitride-oxide-silicon (SONOS) electrically era sable programmable read-only memory (EEPROM) device, which eliminated off-cell leakage current, has been described and fabricated. The leaka ge current is easily encountered in metal-nitride-oxide-silicon (MNOS) -type EEPROMs. Two parasitic transistors, which are in parallel with t he desired variable V(t) cell, are responsible for the leakage current . We demonstrated that the parasitic transistors are caused either by the nearly constant-threshold-voltage parasitic transistors surroundin g the active region or by the ''fringing effect'' in poly-Si gate edge s. The on-state and off-state I-V curves of the cell are shown and com pared with those of two other different devices. The results reveal th at the off-cell leakage current, which is observed in the other two de vices, is completely eliminated in the proposed cell.