Patent ID: 7397705

Claim:
A method for operating a selected cell in an array of charge-trapping cells, wherein the selected cell includes first and second charge trapping sites programmable to different threshold voltages, including a lower level threshold and a higher level threshold, which represent programmed states, comprising: programming the first charge trapping site in the selected cell to a programmed state corresponding to the lower level threshold voltage range, said programming includes applying a first programming scheme adapted to setting a threshold voltage for the first charge trapping site at a level below the lower level threshold voltage range, and applying a second programming scheme adapted to setting the threshold voltage for the first charge trapping site within the lower level threshold voltage range; and programming the second charge trapping site in the selected cell to a programmed state corresponding to the higher level threshold voltage range, said programming includes applying a first programming scheme adapted to setting a threshold voltage for the second charge trapping site within the higher level threshold voltage range.