Patent ID: 7037785

Claim:
A method of manufacturing flash memory device, comprising: (a) sequentially forming a tunnel oxide film, a first polysilicon film and a hard mask film on a semiconductor substrate; (b) etching the hard mask film, the first polysilicon film, the tunnel oxide film and the semiconductor substrate through a patterning process to form a trench within the semiconductor substrate; (c) depositing an oxide film to bury the trench and then polishing the oxide film by means of a chemical mechanical polishing process until the hard mask film is exposed; (d) removing the hard mask film; (e) implementing a cleaning process so that the oxide film is recessed to an extent that a portion of a sidewall of the first polysilicon film is exposed but so that the bottom portion of the sidewall of the first polysilicon film is not exposed and remains covered by the oxide film; (f) depositing a second polysilicon film on the resultant structure and then polishing the second polysilicon film until the oxide film is exposed; (g) forming a dielectric film on the second polysilicon film; and (h) forming a control gate on the dielectric film.