A method of making a flash memory includes providing a substrate. Then, a first insulating layer, a first conductive layer and a second insulating layer are formed to cover the substrate. Later, a first trench is formed in the first conductive layer and the second insulating layer. After that, a second conductive layer and a mask layer are formed to cover the second insulating layer, and the second conductive layer fills up the first trench. Then, the mask layer are patterned to form patterned mask layers. Subsequently, a spacer is formed on the sidewall of the patterned mask layer. Then, an etching process is carried out by using the patterned mask layers and the spacer as a mask so as to form a first gate structure and a second gate structure.