Patent ID: 7470587

Claim:
A method of manufacturing of a flash memory device, the method comprising: performing a high-concentration ion implantation process on a semiconductor substrate; forming a first oxide film, a first polysilicon film, and a hard mask film over the semiconductor substrate to form a stack structure; etching the semiconductor substrate to form first trenches; forming a second oxide film on sidewalls of the first trenches; forming a second polysilicon film to fill the first trenches; oxidizing a portion of a top surface of the second polysilicon film to form a third oxide film, thereby forming a dielectric film; forming a conductive film to form first and second control gates; and etching the second polysilicon film formed in the first trenches between the first and second control gates using the first and second control gates as a mask, thereby forming a second trench; and filling the second trench with an insulating film to form an isolation structure.