The effects of underlying films on the chemical-mechanical polishing (CMP) removal rate have been studied and characterized. A model for the underlying film mechanical properties such as hardness and Young's modulus, relating to the polishing removal rate was proposed. In addition, a modified shallow trench isolation (STI) process with a thin nitride overcoat has been suggested to eliminate the dishing and oxide remaining on nitride issues. Furthermore, in order to minimize the residual particles and metallic contamination, a modified multi-chemical spray-cleaning process provided for the post-STI CMP cleaning was also studied.