A semiconductor device includes: a fin-type active region extending on a substrate in a first direction; a gate structure extending across the fin-type active region in a second direction, different from the first direction; a source/drain region in the fin-type active region on one side of the gate structure; and first and second contact structures connected to the source/drain region and the gate structure, respectively, wherein at least one of the first and second contact structures includes a seeding layer on at least one of the gate structure and the source/drain region and including a first crystalline metal, and a contact plug on the seeding layer and including a second crystalline metal different from the first crystalline metal, and the second crystalline metal is substantially lattice-matched to the first crystalline metal at an interface between the seeding layer and the contact plug.