A semiconductor device includes a first trench and a second trench, a liner pattern along a portion of side surfaces and along bottom surfaces of the first and the second trenches, respectively, a work function metal in the first and the second trenches and on the liner pattern, respectively, a first barrier metal in the first trench and on the work function metal, and having a first thickness, a second barrier metal in the second trench and on the work function metal, and having a second thickness thicker than the first thickness, and a first fill metal on the first barrier metal.