In a slurry composition and a method of polishing a layer using the slurry composition, the slurry composition includes from about 3 to 20 percent by weight of an abrasive, from about 0.1 to 3 percent by weight of an ionic surfactant, from about 0.01 to 0.1 percent by weight of a nonionic surfactant, from about 0.01 to 1 percent by weight of a polish accelerating agent including an amino acid compound, and a remainder of an aqueous solution including a basic pH-controlling agent and water. The slurry composition including the nonionic surfactant and the polish accelerating agent may be used for speedily polishing a stepped upper portion of a silicon oxide layer, and may also enable a lower portion of the silicon oxide layer to function as a polish stop layer.