Single poly-EEPROM with stacked MIM and n-well capacitor

The new structure of electrically erasable programmable read-only memory (EEPROM), using a capacitor of stacked metal-insulator-metal (MIM) and n-well, is proposed. The oxide capacitance in the n-well region is effectively applied without sacrificing the cell area and the control gate coupling ratio. Therefore, for the same program-voltage rating, the proposed cell allows the EEPROM to have a higher speed handling capability even with a quite small cell size. Measured results show that the programming speed of the proposed cell is almost the same as that of the conventional MIM control gate cell. In an endurance test of 10 000 program/erase cycles, the shift of program threshold voltage is found to be 1.4 V without degradation of read currents.