Methods of fabricating semiconductor devices and semiconductor devices formed thereby

A method of fabricating a semiconductor device, comprising:

• providing a substrate formed with a pad oxide;
• forming first and second dummy gate patterns spaced apart from each other on the pad oxide;
• forming an etch stop layer to cover sidewall surfaces and top surfaces of the first and second dummy gate patterns;
• forming a first interlayer insulating layer on the pad oxide and the etch stop layer;
• planarizing the first interlayer insulating layer to expose the etch stop layer on the first and second dummy gate patterns;
• etching the etch stop layer to expose the top surfaces and upper sidewall surfaces of the first and second dummy gate patterns, thereby forming a groove between the first interlayer insulating layer and the first and second dummy gate patterns;
• forming a gap-filling insulating pattern to fill the groove;
• removing the first and second dummy gate patterns and the pad oxide provided thereunder to form first and second trenches exposing the substrate;
• forming a gate insulating layer on bottom surfaces of the first and second trenches;
• forming first and second gate electrodes on the gate insulating layer;
• forming a second interlayer insulating layer on the first and second gate electrodes, the first interlayer insulating layer, and the gap-filling insulating pattern;
• and
• forming a contact plug connected to the substrate between the first and second gate electrodes through the second interlayer insulating layer.