Patent ID: 7183174

Claim:
A method of manufacturing a flash memory device, the method comprising: providing a semiconductor substrate comprising a first region where a cell region is formed, a second region where a peripheral region is formed, and a third region formed in the peripheral region at the boundary portion of the cell region and the peripheral region; performing a first ion implant process to form a triple well region in the semiconductor substrate of a predetermined region of the first region, wherein an end portion of the triple well region is also formed in the third region; forming a gate oxide film for high voltage on the semiconductor substrate of the third region; forming a pattern for defining an isolation film of the cell region in the first region and a predetermined region of the third region, and forming a first trench only in the first region through patterning using the pattern; forming additional patterns for defining isolation films of the peripheral region in predetermined regions of the second and third regions, performing patterning through the additional patterns to form a second trench deeper than the first trench only in the second region, wherein in the patterning for forming the first and second trenches, a dummy active region is formed in the third region in which the patterning is prevented; forming an insulating film for trench burial only within the first and second trenches, thus forming a first isolation film in the first region and a second isolation film, which is deeper than the first isolation film, in the second region; forming a gate oxide film for low voltage on the entire surface except for the dummy active region after forming the first and second isolation films; and forming a first polysilicon film for a floating gate electrode on the entire surface, patterning the first polysilicon film to form the floating gate electrode in the first region and a patterned polysilicon film in the third region, wherein the gate oxide film for high voltage and the patterned polysilicon film are stacked on the dummy active region.