Semiconductor devices

A semiconductor device, comprising:

• a substrate extended in a first direction, comprising an active region and a field region;
• a plurality of gate structures arranged spaced apart from each other in the first direction on the substrate, each gate structure comprising:
• a gate insulating layer pattern on an upper surface of the substrate;
• and
• a gate electrode on an upper surface of the gate insulating layer pattern,
• wherein the gate insulating layer pattern includes an extended portion protruding away from the sidewall of the gate electrode, and
• wherein the extended portion of the of the gate insulating layer pattern has an upper surface and a side surface,
• a capping layer pattern on a sidewall of each gate electrode and on the upper surface of the extended portion of each gate insulating layer pattern;
• a trench exposing a sidewall of the capping layer pattern between the gate structures, wherein the trench has a bottom portion lower than the upper surface of the substrate;
• an insulating layer on the gate structures and the trench;
• a protecting layer on the insulating layer;
• and
• an air gap surrounded by the insulating layer between the gate structures,
• wherein a portion of the insulating layer is formed along the sidewall of each gate structure to cover the sidewall of the gate structure between the gate structure and the air gap,
• wherein the insulating layer has a planarized upper surface, and
• wherein a bottom of the air gap is higher than a bottom surface of the gate insulating layer.