Methods of manufacturing flash memory cells. During a cleaning process
after an etching process for forming a control gate is performed, polymer
remains at the sidewall of a tungsten silicide layer. Therefore, the
sidewall of the tungsten silicide layer is protected from a subsequent a
self-aligned etching process. In addition, upon a self-aligned etching
process, the etch selective ratio of the tungsten silicide layer to a
polysilicon layer is sufficiently obtained using a mixed gas of
HBr/O.sub.2. Therefore, etching damage to the sidewall of the tungsten
silicide layer can be prevented. As a result, reliability of the process
and an electrical characteristic of the resulting device are improved.
