A 128 K flash EEPROM using double-polysilicon technology

An easily manufacturable 128 K flash EEPROM (electrically erasable programmable read-only memory) was developed based on a novel cell. Programming is achieved through hot-electron injection and erasing through electron tunneling from the floating gate to the drain. The cell is 20% larger than an EPROM cell and contains an integral series transistor which ensures selflimited erasing, reduces leakage, and increases the cell current. The flash EEPROM device can withstand thousands of program/erase cycles. Endurance failures are due to threshold window closing caused by electron trapping in the gate oxide. Typical erasure time is 1 s to clear the entire memory.