A semiconductor device including an insulating structure, and a conductive structure in the insulating structure may be provided. The conductive structure includes a barrier layer, an anti-migration layer on the barrier layer, a liner on the anti-migration layer, a conductive layer on the liner, and a capping layer covering a top surface of the barrier layer and a top surface of the anti-migration layer. The capping layer and the liner include Co. The anti-migration layer includes Mn.