Abstract: An electric conductive film is formed on the insulating surface of a substrate, the substrate having a trench formed on the insulating surface, and the conductive film being filled in the trench. Chemical mechanical polishing is executed to expose the insulating surface of the substrate and leave a portion of the conductive film in the trench. The surface of the substrate having the exposed conductive film in the trench and the exposed insulating surface is exposed to first liquid. After being exposed to the first liquid, the surface of the substrate is exposed to second liquid. The first liquid is either solution which contains at least one first substance selected from a first group consisting of benzotriazole, derivative of benzotriazole and interfacial active agent, or water. The second solution is solution which contains the first substance at a density higher than a density of the first liquid.