To enable a conductive line formed in a patterned insulator layer to be improved in thickness uniformity.

First, a thin (50 to 500) metal layer 142 of Vb metal, preferably niobium is formed on a patterned insulator layer 140. Then, a layer 148 of Al or Al, alloy is formed on the thin niobium layer. The aluminum layer 148 is subjected to chemical and mechanical polishing with oxide acid colloidal alumina slurry to make a niobium liner 142 exposed and oxidized. The niobium liner 142 functions as a polishing stop layer. Then, the exposed thin niobium liner 142 is removed by chemical and mechanical polishing. Or a thin layer of Vb metal or its alloy in place of niobium can be made to serve as a liner.