The role of abrasives and additives in ceria-based dispersions on the removal rate of silicon nitride film during chemical mechanical polishing is discussed. Our results suggest that ceria abrasives give high silicon nitride removal rates due to the reactivity of Ce(3+) on the surface of the ceria abrasives with the suboxide formed on the silicon nitride surface by hydrolysis. Also, it was observed that the nitride removal rates were suppressed to <2 nm/min when either the hydrolysis of the nitride to oxide is hindered or the Ce(3+) on the surface of the ceria abrasive is completely blocked by the adsorption of the additives. However, the two polymer additives, poly(4-vinyl pyridine) and poly(acrylic acid-co-diallyldimethyl ammonium chloride), do not suppress the silicon nitride RR even though they adsorb on the ceria particle surface and we propose an alternate removal mechanism for this case. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3596181] All rights reserved.