Method of forming a floating gate in a flash memory device

摘要

The present invention relates to a method of forming a floating gate in a flash memory device. Upon formation of a device isolation film, a space of a lower polysilicon layer for a floating gate is defined, a bird's beak is formed on an internal surface of a trench by subsequent well sacrificial oxidization process and well oxidization process and an upper polysilicon layer for a floating gate is then formed, so that the space of the floating gate is formed. Therefore, the present invention can reduce the cost since a mask process is not required compared to an existing stepper method and the process cost since a planarization process using chemical mechanical polishing process (CMP) is not required compared to the self-aligned floating mode.