A flash memory device and a method of programming a flash memory device include selecting bit lines connected to program cells of multiple memory cells coupled to a selected word line. The selected bit lines are driven to a bit line program voltage through a write driver circuit connected to first ends of the selected bit lines. The selected bit lines are also driven to the bit line program voltage through a bit line detecting/driving circuit connected to second ends of the selected bit lines. The bit line detecting/driving circuit activates the selected bit lines synchronously with voltage variations of the selected bit lines.