Polishing slurry and polishing method

A polishing method comprising;na process of preparing a substrate havingan interlayer insulating layer carrying a surface composed of a concave portion and a convex portion,a barrier layer coating the interlayer insulating layer along its surface, anda conductive substance layer filling the concave portion and coating the barrier layer,a first polishing process of polishing the conductive substance layer to expose the barrier conductor layer on the convex portion of the interlayer insulating layer and the conductive substance layer filling the concave portion of the interlayer insulating layer,a second polishing process of polishing the exposed barrier layer and the exposed conductive substance layer on the concave portion to expose the convex portion of the interlayer insulating layer, the barrier layer coating the concave portion of the interlayer insulating layer and the conductive substance layer filling the concave portion while feeding a polishing slurry, anda third polishing process of over polishing a part of the convex portion of the interlayer insulating layer,wherein the polishing slurry comprises a surfactant, a metal oxide dissolving agent and water,wherein the second polishing process and the third polishing process are conducted in one step, andwherein the surfactant is at least one selected from perfluoroalkanesulfonic acids and derivatives thereof.