NAND flash memory devices and methods of fabricating the same

A NAND includes a device isolation pattern disposed in a region of a substrate defining a plurality of active regions. Memory transistors having memory gate patterns, constituting a cell string, cross the plurality of active regions. Select transistors are disposed over the memory transistors, and lower plugs are disposed on each side of the cell string to electrically connect the plurality of active regions on both sides of the cell string and the select transistors.