THREE-DIMENSIONAL NAND MEMORY DEVICE AND FABRICATION METHOD

A method of forming a three-dimensional (3D) NAND memory device includes: forming a gate line slit through alternating layers of an oxide layer and a conductive material layer, wherein the conductive material layer is further formed on a sidewall and a bottom of the gate line slit; performing a first etch process to remove portions of the conductive material layer from the sidewall and the bottom of the gate line slit and from between adjacent oxide layers, thereby exposing portions of the oxide layer in the gate line slit; removing the exposed portions of the oxide layer on the sidewall of the gate line slit; and performing a second etch process to remove residues of the conductive material layer in the gate line slit.