A semiconductor memory devices and a method of fabricating the same includes sequentially stacking a tunnel insulating layer, a first nano-grain film, a conductive layer for a floating gate, and a second nano-grain film over a semiconductor substrate, forming a trench by etching the second nano-grain film, the conductive layer for the floating gate, the first nano-grain film, the tunnel insulating layer, and the semiconductor substrate, gap-filling the trench with an insulating layer, thus forming an isolation layer, and forming a third nano-grain film on sidewalls of the conductive layer for the floating gate.