PURPOSE: To prevent overpolishing with a process shortened by coating a bumped insulating film with a polishing protective film of slower polishing speed and by selectively removing the polishing protective film on a bump by polishing and that on a successive insulating film bump.

CONSTITUTION: The whole of a bumped insulating film formed over a base semiconductor substrate 1 with a plurality of convex patterns 3 is coated with a polishing protective thin film 5 made of a material whose polishing speed is slower than that of the insulating film 6 at least. Then, polishing is conducted to selectively remove the polishing protective thin film 5 on the bumps 3, and further polishing is conducted to selectively remove the bumps on the surface of the insulating film 6. A polishing speed is automatically decreased by exposing a polishing protective film 4 kept formed over the surface of the base bumped pattern 3. For example, the insulating film 6 should be a BPSG layer, and the polishing protective films 4, 5 silicon oxide films.