Semiconductor devices are provided. A semiconductor device includes a first active pattern on a first region of a substrate, a pair of first source/drain patterns on the first active pattern, a first channel pattern between the pair of first source/drain patterns, and a gate electrode that extends across the first channel pattern. The gate electrode is on an uppermost surface and at least one sidewall of the first channel pattern. The gate electrode includes a first metal pattern including a p-type work function metal, a second metal pattern on the first metal pattern and including an n-type work function metal, a first barrier pattern on the second metal pattern and including an amorphous metal layer that includes tungsten (W), carbon (C), and nitrogen (N), and a second barrier pattern on the first barrier pattern. The second barrier pattern includes the p-type work function metal.