A semiconductor device and a method of fabricating the same are provided. The semiconductor device includes a substrate including a first region and a second region, a first transistor and a second transistor formed on the first region and the second region, respectively, a first contact formed on the first transistor, and a second contact formed on the second transistor. The first contact includes a first work function control layer having a first thickness and a first conductive layer formed on the first work function control layer, the second contact includes a second work function control layer having a second thickness different from the first thickness and a second conductive layer formed on the second work function control layer, and the first contact and the second contact have different work functions.