A method for fabricating a semiconductor device includes forming a fin type pattern protruding from a substrate and extending in a first direction, forming a field insulating layer covering a limited portion of the fin type pattern on the substrate such that the field insulating layer exposes a separate limited portion of the fin type pattern, forming a gate structure on the field insulating layer and the fin type pattern, the gate structure extending in a second direction, the second direction different from the first direction, forming a first barrier layer containing a nitrogen element in a first region of the field insulating layer, wherein the first region is exposed by the gate structure, adjacent to the gate structure and extending in the second direction and forming a gate spacer on the first barrier layer and on a side wall of the gate structure.