A method of fabricating a semiconductor device includes forming an active pattern protruding from a substrate, forming a liner layer on the active pattern, forming a sacrificial gate pattern on the liner layer and crossing the active pattern, forming source/drain regions on the active pattern and at both sides of the sacrificial gate pattern, forming an interlayer insulating layer to cover the source/drain regions, forming capping insulating patterns on the interlayer insulating layer to expose the sacrificial gate pattern, and removing the sacrificial gate pattern and the liner layer by an etching process using the capping insulating patterns as an etch mask to form a gap region exposing the active pattern. The active pattern includes a material having a lattice constant greater than a lattice constant of the substrate, and the capping insulating patterns include a material having an etch selectivity with respect to the liner layer.