Abstract: A method of forming an isolation layer of a semiconductor device includes forming first trenches in an isolation region of a semiconductor substrate. A spacer is formed on sidewalls of each of the first trenches. Second trenches are formed in the isolation region below the corresponding first trenches. Each second trench is narrower and deeper than the corresponding first trench. A first oxide layer is formed on sidewalls and a bottom surface of each of the second trenches. The first trench is filled with an insulating layer.

Abstract: A method of manufacturing a semiconductor device includes the steps of forming an interlayer insulating layer and an etch-stop nitride layer over a semiconductor substrate, etching the etch-stop nitride layer and the interlayer insulating layer to form contact holes, forming contacts in the contact holes, forming an oxide layer on the entire surface including the contacts, etching the oxide layer using the etch-stop nitride layer as a target, thus forming trenches through which the contacts and the etch-stop nitride layer adjacent to the contacts are exposed, and forming bit lines in the trenches.

Abstract: A method of manufacturing semiconductor devices includes forming a trench in a predetermined region of a substrate. A first insulating layer and a second insulating layer are formed on a entire surface so that the trench is gap-filled. The first and second insulating layers are polished until a top surface of the substrate is exposed. A wet etch process of a low selectivity is performed, so that a portion of the first insulating layer remains on sides of the trench while stripping the second insulating layer. A third insulating layer is formed on the entire surface, so that the trench is gap-filled, thereby forming an isolation structure.