Disclosed is a flash memory device and a method of manufacturing the same. The flash memory device includes a floating gate formed on a semiconductor substrate, a select gate self-aligned on one sidewall of the floating gate, and an ONO pattern interposed between the floating gate and the select gate. A self-aligned split gate structure is formed for an EEPROM tunnel oxide cell flash memory device employing a split gate structure, so that a cell current is constant and the erasing characteristic between cells is uniform, thereby improving the reliability.