A semiconductor device includes an interlayer dielectric layer on a substrate, a first connection line that fills a first trench of the interlayer dielectric layer, the first trench having a first width, and a second connection line that fills a second trench of the interlayer dielectric layer, the second trench having a second width greater than the first width, and the second connection line including a first metal layer that covers an inner sidewall of the second trench, a barrier layer that covers a bottom surface of the second trench, and a second metal layer on the first metal layer and the barrier layer, the first connection line and the first metal layer include a first metal, and the second metal layer includes a second metal different from the first metal.