Pattern density effects during chemical-mechanical planarization (CMP) for shallow trench isolation applications using fixed abrasive pads were investigated in this work. Wafers patterned with various test masks, having a mix of pattern densities, were polished, and their polishing characteristics are correlated to their respective pattern density distributions in the dies. Single patterned density wafers were also polished in order to understand the affect of individual pattern densities on the polish rates as well as "pad activation.'' It was observed that the low pattern density features in a die affected the polishing characteristics of the high pattern density features present on the same die in a wafer. Compared to the high pattern density structures, it was observed that the low pattern density features activated the pad more effectively. (C) 2003 The Electrochemical Society.