A method of fabricating a semiconductor device includes forming a first preliminary gate barrier layer and a first preliminary gate electrode recessed to have a first depth from the surface of the substrate within a gate trench, removing an upper portion of the first preliminary gate electrode by means of a first wet etching process using a first etchant to form a second preliminary gate electrode recessed to have a second depth greater than the first depth, and removing an upper portion of the first preliminary gate barrier layer and an upper portion of the second preliminary gate electrode by means of a second wet etching process using a second etchant to form a gate electrode and a gate barrier layer recessed to a third depth greater than the second depth.