A slurry composition includes about 4.25 to about 18.5 weight percent of an abrasive, about 80 to about 95 weight percent of deionized water, and about 0.05 to about 1.5 weight percent of an additive. The slurry composition may further include a surfactant. In a polishing method using the slurry composition, a polysilicon layer may be rapidly polished, and also dishing and erosion of the polysilicon layer may be suppressed.