Method of forming isolation structure of semiconductor device

Abstract

Provided is a method of forming an isolation structure of a semiconductor device capable of minimizing the number of performing a patterning process and having trenches of various depths. The method includes partially etching the semiconductor substrate using a first patterning process to form first trenches and second trenches having a first depth. The semiconductor substrate has first to third regions. The first trenches are formed in the first region, and the second trenched are formed in the second region. The semiconductor substrate is partially etched using a second patterning process, so that third trenches are formed in the third region, and fourth trenches are formed in the second region. The fourth trenches extend from bottoms of the second trenches. The third trenches have a second depth, and the fourth trenches have a third depth. An isolation layer filling the first to fourth trenches is formed.