In a wiring forming method according to the present invention, an insulating layer is formed on a semiconductor substrate, and contact holes are formed in the insulating layer. A titanium layer is deposited on the insulating layer so as to be along inner surfaces of the contact holes. A first titanium nitride layer is formed on the titanium layer including the titanium layer formed in the contact holes. The deposition of the first titanium nitride layer is carried out under atmosphere which substantially includes no oxygen. A titanium oxynitride layer is deposited on the first titanium nitride layer. A second titanium nitride layer is deposited on the titanium oxynitride layer. Buried plugs are formed on the second titanium nitride layer formed in the contact holes. A wiring connected to the buried plugs are formed on the insulating layer. A barrier metal layer and the buried plugs are thus formed in the contact holes. According to such the structure, a stable electric contact can be obtained.