Method for programming multi-level cell flash memory device

[0027]A method for programming a multi-level cell (MLC) flash memory device in accordance with embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0028]A program operation of a flash memory device includes injecting electrons to a floating gate of a selected memory cell transistor and verifying whether a threshold voltage of the programmed memory cell transistor reaches a predetermined threshold voltage. The injecting of the electrons and the verifying of the predetermined threshold voltage are repeated on selected memory cells within a predetermined number of program operations until the predetermined threshold voltage is reached.

[0029]To obtain an MLC structure, it is important that the width of threshold voltage distribution in each programmed status is uniform and narrow within predetermined limits. Specifically, a program operation levels a threshold voltage of a memory cell in a [11] state (i.e., an erased state) to above