A method of chemical-mechanical polishing (CMP) and a method of forming an isolation layer using the same are provided. The method of chemical-mechanical polishing includes performing a first chemical-mechanical polishing operation on an insulating layer having a zeta potential with a first polarity by supplying a first slurry on the insulating layer, wherein the first slurry includes a first abrasive and ionic surfactants having a zeta potential with a second polarity opposite to the first polarity. The method of forming an isolation layer includes forming a mask layer on a substrate, etching the substrate to a desired depth using the mask layer such that a trench is formed in the substrate, forming the insulating layer on the substrate and performing the first chemical-mechanical polishing operation described above.