Method for manufacturing a semiconductor device having a silicide region comprised of a silicide of a nickel alloy

To provide a semiconductor device which can reduce an electrical resistance between a plug and a silicide region, and a manufacturing method thereof. At least one semiconductor element having a silicide region, is formed over a semiconductor substrate. An interlayer insulating film is formed over the silicide region. A through hole having an inner surface including a bottom surface comprised of the silicide regions is formed in the interlayer insulating film. A Ti(titanium) film covering the inner surface of the hole is formed by a chemical vapor deposition method. At least a surface of the Ti film is nitrided so as to form a barrier metal film covering the inner surface. A plug is formed to fill the through hole via the barrier metal film.