In a method of manufacturing a semiconductor device, a gate space is formed by removing a sacrificial gate electrode, a gate dielectric layer is formed in the gate space, conductive layers are formed on the gate dielectric layer to fully fill the gate space, the gate dielectric layer and the conducive layers are recessed to form a recessed gate electrode, and a contact metal layer is formed on the recessed gate electrode. The recessed gate electrode does not includes tungsten, and the contact metal layer includes tungsten.