Method of forming an isolation layer, method of manufacturing a semiconductor device using the same, and semiconductor device having an isolation layer

A method of manufacturing a semiconductor device, comprising:

• forming a plurality of trenches on a substrate including a cell region and a peripheral region, the trenches having aspect ratios different from each other;
• forming a liner on inner walls of the trenches;
• thermally oxidizing the liner to fill up some of the trenches having relatively high aspect ratios to form a first isolation layer;
• filling up the other trenches having relatively low aspect ratios with an insulation material to form a second isolation layer;
• forming a gate structure on the substrate having the first and second isolation layers thereon;
• forming an impurity region at an upper portion of the substrate;
• and
• forming a capacitor to be electrically connected to the impurity region.

A semiconductor device comprising:

• a first isolation layer including a nitride liner and an oxynitride layer sequentially stacked on a substrate, the substrate including a cell region and a peripheral region;
• a second isolation layer including the nitride liner, the oxynitride layer and an SOG layer sequentially stacked on the substrate;
• a gate structure on the substrate having the first and second isolation layers thereon;
• an impurity region at an upper portion of the substrate;
• and
• a capacitor electrically connected to the impurity region.