One embodiment of a method of fabricating a flash memory device includes forming a trench mask pattern, which includes a gate insulation pattern and a charge storage pattern stacked in sequence, on a semiconductor substrate; etching the semiconductor substrate using the trench mask pattern as an etch mask to form trenches defining active regions; and sequentially forming lower and upper device isolation patterns in the trench. After sequentially forming an intergate insulation film and a control gate film on the upper device isolation pattern, the control gate film, the intergate insulation pattern and the gloating gate pattern are formed, thereby providing gate lines crossing over the active regions.