Patent ID: 6822898
Filing Date: 2004-11-23
Classification: G11C

Abstract:
A multi-value nonvolatile semiconductor memory device comprising a multi-value memory cell having a floating gate and able to store at least three values,wherein the threshold values of the multi-value memory cell are set from a state in which the threshold values designate at least two boundary values that identify at least three values to a state in which the threshold values are increased by the injection of a predetermined quantity of charges into the floating gate in a data write operation, wherein the read data is determined from the relationship between the threshold values of the multi-value memory cell and the at least two boundary values, and wherein the increment in the threshold value from the state in which the threshold values of the multi-value memory cell designate the at least two boundary values to the state in which the threshold values are increased by the injection of charges into the floating gate in the data write operation is larger for data corresponding to a state in which a larger quantity of charges are injected.