A method of manufacturing a NAND flash memory device, including the steps of forming gates over a semiconductor substrate; forming a junction region over the semiconductor substrate between the gates; forming a buffer oxide film on the gates and the semiconductor substrate; stripping the buffer oxide film at one side of the gates; forming a nitride film spacers over the sidewalls of the gates; forming a self-aligned contact process (SAC) nitride film and an insulating film over the entire structure; etching regions of the insulating film and the SAC nitride film to form a contact through which the junction region is exposed; and forming a conductive film to bury the contact, thereby forming a contact plug.