An integrated circuit (IC) device includes a semiconductor substrate having a via hole extending through at least a part thereof, a conductive structure in the via hole, a conductive barrier layer adjacent the conductive structure; and a via insulating layer interposed between the semiconductor substrate and the conductive barrier layer. The conductive barrier layer may include an outer portion oxidized between the conductive barrier layer and the via insulating layer, and the oxidized outer portion of the conductive barrier layer may substantially surrounds the remaining portion of the conductive barrier layer.