Abstract
In the invented manufacturing method of selection gate for the split gate flash memory cell, the selection gate is formed on the trench sidewall of the semiconductor substrate to shrink the lateral dimension of the selection gate and maintain the channel length. The manufacturing method of the selection gate at least contains the followings: forming a trench in the semiconductor substrate at one side of the floating gate structure; forming an intermediate polysilicon dielectric layer on the floating gate structure and on the trench sidewall; and forming a polysilicon spacer on the sidewall of the intermediate polysilicon dielectric layer for use as the selection gate. The split-gate type flash memory cell can generate the trajectory hot electrons to improve data write-in efficiency and decrease the write-in voltage.