Non-volatile memory device and method of programming the same

A method of programming a vertical NAND (VNAND) flash memory system comprising a NAND flash memory device including a plurality of memory cells, which are stacked in a vertical direction over a substrate and connected to word lines, and a memory controller configured to control a program order of the VNAND flash memory device, the method comprising:

• sequentially programming memory cells of a first region including an N-th word line, from memory cells of the N-th word line to memory cells of a word line disposed farthest from the N-th word line, wherein N is an integer greater than or equal to 2;
• and
• programming memory cells of an N−1-th word line after the programming of the memory cells of the first region,
• wherein a maximum value of threshold voltages of the memory cells of the N−1-th word line is equal to or lower than a maximum value of threshold voltages of the memory cells of the N-th word line.