A trapping gate forming process includes the following. An oxide/nitride/oxide layer is formed on a substrate. A hard mask is formed to cover the oxide/nitride/oxide layer. The hard mask, the oxide/nitride/oxide layer and the substrate are patterned to form at least a trench in the hard mask, the oxide/nitride/oxide layer along a first direction. An isolation structure is formed in the trench. A first gate is formed across the oxide/nitride/oxide layer along a second direction orthogonal to the first direction. A flash cell formed by said process includes a substrate, a first gate and an oxide/nitride/oxide layer. The substrate contains at least an active area extending along a first direction. The first gate is disposed across the active area along a second direction orthogonal to the first direction, thereby intersecting an overlapping area. The oxide/nitride/oxide layer is disposed in the overlapping area between the first gate and the active area.