A method for forming a shallow trench isolation structure within a semiconductor substrate includes forming a trench opening within a semiconductor substrate having an oxidation-resistant material as a top surface. An oxide liner is formed on inner surfaces of the trench opening. A silicon material is then introduced into the trench opening and over the top surface. The silicon material is subsequently oxidized, either before or after a polishing operation is used to planarize the structure. Dishing related problems are avoided during polishing because the silicon or oxidized silicon material has a polishing rate similar to the oxidation resistant material, and less than that of conventionally formed CVD oxides.