Method of programming non-volatile semiconductor memory device having an electrically erasable and programmable memory cell array

Abstract

A non-volatile semiconductor memory device includes a memory cell array in which electrically erasable and programmable memory cells are arrayed, each of the memory cells storing therein a first logic state with a threshold voltage lower than or equal to a first value or a second logic state with a threshold voltage higher than or equal to a second value that is higher than the first value, a data hold circuit for holding program data and sensing data as read out of the memory cell array, and a controller configured to control a program sequence, wherein the controller has the control functions of: a program control function for applying a program voltage to a selected memory cell of the memory cell array to let the data shift from the first logic state to the second logic state; a program verify control function for verifying that the programmed data of the selected memory cell shifted to the second logic state; an erratic program verify control function for checking that the threshold voltage of a memory cell to be held in the first logic state does not exceed a third value set as an upper limit value of a variation of the first logic state; and an over-program verify control function for checking that the threshold voltage of the selected memory cell shifted to the second logic state does not exceed a fourth value set as an upper limit thereof.

Dependencies are inferred from the claim text.