Semiconductor device including device isolation layer with multiple patterns

Abstract

A semiconductor device includes a substrate having one or more inner surfaces defining trenches that define an active pattern of the substrate, the trenches including a first trench and a second trench which have different widths, a device isolation layer on the substrate such that the device isolation layer at least partially fills the trenches, and a word line intersecting the active pattern. The device isolation layer includes a first isolation pattern covering a portion of the second trench, a second isolation pattern on the first isolation pattern and covering a remaining portion of the second trench, and a filling pattern filling the first trench under the word line. A top surface of the second isolation pattern is located at a higher level than a top surface of the filling pattern.