Method of manufacturing semiconductor device

An object of the present invention is to provide a method for manufacturing a semiconductor device wherein a contaminant containing a fluorine-containing polymer is removed from an exposed copper surface to provide such a state that a native oxide film is formed on the copper surface, thereby suppressing the copper from being corroded. A method to achieve the above object is described as follows. After forming a first wiring layer on a semiconductor substrate, a silicon nitride film is formed on the first wiring layer. Then, a second interlayer insulating film is formed on the silicon nitride film. The second interlayer insulating film is etched to expose the silicon nitride film, and then the exposed silicon nitride film is etched by a fluorine-containing gas to form a via hole. A plasma treatment is carried out on an exposed first copper layer to remove a contaminant containing a fluorine-containing polymer. Then, a second barrier metal film and a second copper layer is stacked inside the via hole to form a via plug.