METHOD OF FORMING FLOATING GATE OF FLASH MEMORY DEVICE USING BUFFER OXIDE LAYER FOR PREVENTING DECREASE OF THICKNESS IN FIRST POLYSILICON LAYER AND RESTRAINING ATTACK AGAINST FIRST POLYSILICON LAYER

摘要

PURPOSE: A method of forming a floating gate of a flash memory device is provided to prevent the decrease of thickness of a first polysilicon layer and to restrain the attack against the first polysilicon layer during a pad nitride layer stripping process by forming a buffer oxide layer with minimum thickness between the first polysilicon layer and a pad nitride layer. CONSTITUTION: A tunnel oxide layer(12), a first polysilicon layer(14), a buffer oxide layer(16) and a pad nitride layer(18) are sequentially formed on a semiconductor substrate(10). A trench is formed in the resultant structure by using etching. A gap-fill oxide is formed thereon and the resultant structure is planarized by using the pad nitride layer as a barrier. A strip process for removing completely the pad nitride layer and partially the buffer oxide layer is performed thereon. The remaining buffer oxide layer is removed by using a cleaning process.