A non-volatile semiconductor memory device comprises a semiconductor substrate and a plurality of gate structures formed on a cell region of the semiconductor substrate. The plurality of gate structures include a first select-gate and a second select-gate disposed on the cell region, the first select-gate and the second select-gate spaced apart from each other. A plurality of cell gate structures are disposed between the first select-gate and the second select-gate. The first select-gate and an adjacent cell gate structure have no air gap defined therebetween. At least a pair of adjacent cell gate structures have an air gap defined therebetween.