A method of fabricating a flash memory is disclosed. The method begins a stacked gate on the substrate. A shallow junction doping is performed on a substrate having a stacked gate already formed thereon, with the stacked gate serving as a mask, so as to form a shallow junction doped region in the substrate adjacent to both sides of the stacked gate. A mask layer is formed on the substrate to cover a top surface and sidewalls of the stacked gate, while exposing portions of the shallow junction doped region. With the mask layer serving as a mask, a deep junction doping is performed on the substrate to form a deep junction doped region in the substrate adjacent to both sides of the mask layer. After the mask layer is removed, a thermal process is performed to form a source/drain region having both the shallow junction doped region and deep junction doped region.