Patent ID: 6115285
Filing Date: 2000-09-05
Classification: G11C

Abstract:
The memory device adapted for multi-level charge storage, comprising:a plurality of flash EEPROM memory cells including a source region, a drain region, a channel region and a floating gate, said floating gate including first and second floating gate portions, said first floating gate portion extending over said channel region, said second floating gate portion extending away from said channel region, said flash EEPROM memory cells further including a program gate and a control gate, said program gate forming a capacitor with said second floating gate portion;readout means for parallel outputting binary data corresponding to charge levels stored in said flash EEPROM memory cells; andprogramming means for applying a low voltage to said control gate, for applying a voltage not greater than 5 Volts to said drain region and for applying a high voltage pulse with a predetermined amplitude, selected from a plurality of predetermined amplitudes and with an essentially fixed time width to said program gate, said predetermined amplitudes determining said charge levels,said plurality of flash EEPROM memory cells being arranged in an array with rows and columns having drains of the flash EEPROM memory cells belonging to a same column connected together whereby forming a data output line;the program gates of the flash EEPROM memory cells belonging to the same column being connected together whereby forming a data input line; andthe control gates of the flash EEPROM memory cells belonging to the same row being connected together whereby forming a word line,said data input line and said data output line being essentially parallel and routed in a same direction; andsaid word line being routed in a direction that is essentially perpendicular to a direction of said data input line and said data output line,wherein said array further comprises:dummy cells on essentially each row of the array, said dummy cells providing reference currents in readout operation.