SEMICONDUCTOR NONVOLATILE MEMORY, CHARGE ACCUMULATION METHOD FOR SEMICONDUCTOR NONVOLATILE MEMORY, AND CHARGE ACCUMULATION PROGRAM

摘要

PROBLEM TO BE SOLVED: To expand a current window by making current value distribution width narrower.SOLUTION: Gate voltage is gradually increased (B) as a write-in frequency increases so that charge is gradually accumulated in charge accumulation sections on a semiconductor substrate. When a value of current flowing in a channel region has become such a value that an amount of the charge to be accumulated in the charge accumulation sections corresponds to predetermined data, and when the value of the current approaches a target value in a region where the current flowing in the channel region is greater than the predetermined target value, an increase rate in a charge accumulation amount per one time is decreased (C) by lowering source voltage and drain voltage. Thus, exceeding the target value, of the charge accumulation amount to each charge accumulation section is suppressed.