Single poly eeprom allowing continuous adjustment of its threshold voltage

Abstract

A single-poly EEPROM memory device comprises a control gate isolated within a well of a first conductivity type in a semiconductor body of a second conductivity type, first and second tunneling regions isolated from one another within respective wells of the first conductivity type in the semiconductor body, a read transistor isolated within a well of the first conductivity type, and a floating gate overlying a portion of the control gate, the read transistor, and the first and second tunneling regions. The memory device is configured to be electrically programmed by changing a charge on the floating gate that changes the device threshold voltage. In one embodiment, the memory device is configured to be electrically programmed by applying a first potential between the first and second tunneling regions, and a second potential to the control gate, the second potential having a value less than the first potential.

1 . A method of electrically programming a memory device, comprising:
 providing the memory device comprising a floating gate overlying first and second tunneling regions, a control gate, and a read transistor;   applying a first potential to the first tunneling region;   applying a second potential to the second tunneling region; and   applying a third potential to the control gate to induce a charge on the floating gate thereby electrically programming a threshold voltage Vt of the memory device.   
   
   
       2 . The method of  claim 1 , wherein the first and second potentials are different, and wherein the third potential has a value which is between the first and second potentials. 
   
   
       3 . The method of  claim 1 , wherein the memory device comprises one of a single-poly EEPROM, and a modified OTP EPROM.