| CPC H01L 29/785 (2013.01) [H01L 21/76224 (2013.01); H01L 29/66545 (2013.01); H01L 29/66795 (2013.01)] | 20 Claims |
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1. A method of forming an isolation structure, the method comprising:
removing an upper portion of a substrate to form active fins spaced apart from each other in a second direction on the substrate, each of the active fins extending in a first direction parallel to an upper surface of the substrate, and the second direction being parallel to the upper surface of the substrate and crossing the first direction;
forming a first isolation pattern on the substrate to cover sidewalls of the active fins;
partially removing the active fins and the first isolation pattern and the upper portion of the substrate to form an opening having a bottom lower than a lower surfaces of each of the active fins and a lower surface of the first isolation pattern;
forming a second isolation pattern to fill the opening;
partially removing the active fins, the first isolation pattern, the second isolation pattern and the upper portion of the substrate to form a recess having a bottom lower than the lower surfaces of each of the active fins, and the lower surface of the first isolation pattern, and a lower surface of the second isolation pattern, the recess defining an active region on the substrate;
forming a third isolation pattern to fill the recess; and
removing upper portions of each of the first isolation pattern, the second isolation pattern, and the third isolation pattern to expose upper portions of the active fins,
wherein the active region includes a first sidewall and a second sidewall opposite to each other in the second direction, and
wherein the first sidewall of the active region includes a lower portion contacting the third isolation pattern and an upper portion contacting the second isolation pattern, and has a staircase shape.
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