Method of eliminating dishing effect in polishing of dielectric film

A method of forming a dishing free conductive structure, said method comprising:

• patterning a conductive structure having a first gap with a first width and a second gap with a second width formed between thereof, wherein said first width is wider than said second width;
• coating a spin-on-material on said conductive structure;
• performing a thermal treatment to convert said spin-on-material into an oxide, thereby forming the lowest surface over said first gap to be higher than the surface of said conductive structure;
• polishing said spin-on-material by chemical mechanical polishing, wherein said lower surface of said converted spin-on-material layer is higher than said surface of the conductive layer to prevent said first gap from being attacked by a slurry or a pad used during chemical mechanical polishing, wherein said second gap can be planarized such that its top surface is substantially planar with the top surface of said conductive structure, a first portion of said spin-on-material over said second gap is completely removed, and a second portion of said spin-on-material remains over said first gap, thereby reducing dishing effect.