Method of forming a gate in a stack gate flash EEPROM cell

Abstract

The present invention relates to a method of forming a gate in a stack gate flash EEPROM cell. In order to preventing a lateral bird's beak from occurring in an ONO dielectric layer during a reoxidation process to be performed after a formation of a cell gate having a stack structure formed by stacking a floating gate, an ONO dielectric layer and a control gate, an oxide layer and a nitride layer are sequentially formed on an entire structure before the reoxidation and after a formation of the cell gate. The oxide layer serves to reduce a stress in depositing the nitride layer, and the nitride layer serves to prevent an occurrence of the lateral bird's beak of the ONO dielectric layer during the reoxidation process. Accordingly, the present invention prevents the lateral bird's beak of the ONO dielectric layer, thereby improving a speed of cell erase operation.

Dependencies are inferred from the claim text.