A NAND flash memory array, an operating method and a fabricating method of the same are provided. The NAND flash memory array has a cut-off gate line under a control gate in order to operate two cells having vertical channels independently with one control gate (i.e., a shared word line). The memory cell area is reduced considerably compared to the conventional vertical channel structure, and is better for high integration. A shared cut-off gate turn off is made during a programming operation and prevents programming the opposite cell by a self-boosting effect. It is possible to shield electrically with a shared word line (a control gate) during a reading operation, and minimizes the effect of storage condition of the opposite cell. Also, the NAND flash memory array can be fabricated by using the conventional CMOS process.