A floating gate transistor, muti-level cell memory device and method for programming the cells and stabilizing the programmed charge

摘要

This invention relates to a method and device for programming and stabilizing a multi-level cell Flash memory device, in which the cells have a number of possible states higher than two, each state corresponding to an allowable threshold voltage range for the transistor of the cell as established by a pair of reference voltages, variable as a function of the cell ageing, said cells being programmed, starting from a full erasure state, by injection of a charge into the floating gate; said method comprises a first programming step for ascertaining the characteristics of the individual cells and one or more subsequent programming steps in which pulses are applied to each cell, the number and the amplitudes of said pulses being individually selectable for each cell, said method further providing that the charge in the individual cells be reset by said stabilization step. <IMAGE>