The relative SiO2 and Si3N4 material removal rates during chemical mechanical planarization were varied by three orders of magnitude as a function of water soluble organic additives in aqueous ceria suspensions. The Si3N4 removal requires a hydrolysis step which is influenced by the additive acid-base characteristics. The additives are postulated to stabilize the Si3N4 surface via site blocking or surface amine deprotonation. Molecules which can adsorb to either silica or ceria surfaces will also decrease SiO2 removal rates. The results highlight the importance of additive functionality in mitigating ceria reactivity with surface silanol groups. (c) 2005 The Electrochemical Society.