A semiconductor device includes a fin-type active region; a gate dielectric layer covering an upper surface and opposite lateral surfaces of the fin-type active region; and a gate line extending on the gate dielectric layer to cover the upper surface and opposite lateral surfaces of the fin-type active region and to cross the fin-type active region. The gate line includes an aluminum (Al) doped metal-containing layer extending to cover the upper surface and opposite lateral surfaces of the fin-type active region to a uniform thickness, and a gap-fill metal layer extending on the Al doped metal-containing layer over the fin-type active region. Related fabrication methods are also described.