A first CVD dielectric layer is deposited on a surface of a semiconductor substrate. Next, low-k layers are deposited in at least two different steps to form one of a via-layer dielectric film and a wiring-layer dielectric film on the first CVD dielectric layer. Immediately after the depositions, thermal treatment is performed. A second CVD dielectric layer is deposited on the low-k layers. A groove is formed in the second CVD dielectric layer and the low-k layers. A metal layer is deposited on that structure, filling the groove. The metal layer is removed from the second CVD dielectric layer by chemical mechanical polishing.