Method of forming trench type isolation film of semiconductor device

A method of forming a trench type isolation film of a semiconductor device, including the steps of sequentially forming a pad oxide film and a nitride film for a hard mask on a semiconductor substrate in which a cell region and a peri region are defined; patterning the nitride film using an etch process employing a cell array mask; coating a photoresist on the entire structure including the patterned nitride film; patterning the photoresist using a peri ISO mask; sequentially etching the nitride film, the pad oxide film, and the semiconductor substrate using the patterned photoresist as an etch mask, thereby forming first trenches; stripping the photoresist; etching the semiconductor substrate of the cell region and the peri region using the patterned nitride film as an etch mask, thereby forming second trenches in the cell region and third trenches, which are consecutive to the first trenches, in the peri region; and, forming an isolation film within the second and third trenches. The invention can prevent dislocation depending the concentration of stress on micro trenches and can improve field leakage characteristics.