A vertical flash memory includes a plurality of vertical memory cells, wherein each of the vertical memory cells includes a selective gate, a main gate, a dielectric interlayer and a vertical channel layer. The selective gate is disposed on a substrate. The main gate is stacked on the selective gate. The dielectric interlayer isolates the main gate from the selective gate. The vertical channel layer is disposed on sidewalls of the selective gate and the main gate. The present invention also provides a method of forming said vertical flash memory.