Methods for fabricating a semiconductor device and semiconductor devices fabricated by the same

A method for fabricating a semiconductor device, the method comprising:

• sequentially forming an etch target layer and a lower mold layer on a substrate, the substrate including a cell array region and a peripheral circuit region and the etch target layer including a separation region;
• forming a first etch stop pattern on the lower mold layer, the first etch stop pattern vertically overlapping the separation region;
• forming an intermediate mold layer on the lower mold layer, the intermediate old layer at least partially covering the first etch stop pattern;
• forming first mold patterns on the intermediate mold layer;
• forming first spacers on sidewalls of the first mold patterns;
• etching the intermediate mold layer using the first spacers as etch masks to form second mold patterns, where portions of the second mold patterns are on the first etch stop pattern;
• forming second spacers on sidewalls of the second mold patterns;
• etching portions of the first etch stop pattern to form second etch stop patterns during the formation of the second spacers;
• etching the lower mold layer using the second spacers and the second etch stop patterns as etch masks to form third mold patterns;
• etching the etch target layer using the third mold patterns as etch masks, to form insulating patterns;
• and
• forming conductive lines in spaces between the insulating patterns.