Patent ID: 7449400

Claim:
A method of forming an isolation film in a semiconductor device, comprising the steps of: providing a semiconductor substrate in which a cell region, a peripheral region and a boundary region of the cell region and the peripheral region are defined; performing a first ion implant process to form a deep well region in a predetermined region of the cell region and a first doped region in a predetermined region of the boundary region; performing a second ion implant process to form a well region shallower than the deep well region within the deep well region of the cell region and a second doped region within the first doped region, thereby defining a doped region having the first doped region and the second doped region in the boundary region; performing a patterning process on predetermined regions of the cell region and the peripheral region to form a first trench having a first depth; performing a patterning process to expose a predetermined region of the peripheral region in which the first trenches is formed, and forming a second trench having a second depth deeper than the first depth only in the peripheral region; and forming an insulating film for trench burial only within the trenches of the result, thereby forming an isolation film having a first depth in the cell region, an isolation film having a second depth in the peripheral region, and an isolation film having a dual depth, which has the isolation film of the first depth and the isolation film of the second depth at the same, in the boundary region.