PROGRAM METHOD CAPABLE OF COMPENSATING READ MARGIN REDUCED DUE TO CHARGE LOSS

摘要

A program method of a flash memory device capable of compensating read margin reduction due to charge loss is provided to assure a sufficient read margin between adjacent states due to electric field coupling/F-poly coupling and HTS(Hot Temperature Stress) by performing second programming on memory cells belonging to a specific region of each state after first programming. According to a program method of a flash memory device comprising a plurality of memory cells for storing multi-bit data indicating one of plural states, memory cells selected to have one state are programmed with the multi-bit data. Programmed memory cells having a threshold voltage which is a voltage between a second verify voltage and one of a first verify voltage and a read voltage are detected. The second verify voltage is higher than the first verify voltage. The detected memory cells are programmed to have a threshold voltage equal to or higher than the second verify voltage corresponding to each state, where the second voltages for different states have different levels.