Provided are a slurry composition for CMP and a polishing method using the same, in which polishing can be performed by freely adjusting the selectivity ratio of a silicon oxide film, a silicon nitride and a polysilicon film through control of the amounts of additive and solvent, and thus the slurry composition can be efficiently applied to the process of manufacturing a semiconductor, requiring selective removal of a silicon nitride film and a polysilicon film relative to a silicon oxide film.