Although poly(acrylic acid) (PAA) has been used as a passivation agent for high polish rate selectivity between SiO2 and Si3N4 in STI CMP, it causes severe dishing during the over-polishing step. Here, we fabricated interpolymer complexes of PAA and poly(ethylene glycol) (PEG) as passivation agent for low dishing as well as high selectivity. PAA and PEG form a cross-linked network structure through H-bonding, which is called an "interpolymer complex". During the over-polishing step, the cross-linked network structure of the PAA-PEG interpolymer complex prevents abrasives from polishing SiO2 in the trenches, resulting in a significant decrease in dishing. These results provide researchers with a new approach toward passivation agents to provide low dishing in STI CMP. (C) 2015 Elsevier B.V. All rights reserved.