We have studied the switching behavior of a single Co/Pt multilayer dot under the assistance of rf fields. The switching field monotonically decreases with increasing rf frequency up to a critical frequency. It is found that the reduction of the switching field is more significant than the theoretical prediction based on the single macrospin model. In addition, switching field distribution due to thermal fluctuation is also considerably suppressed. The simulation has revealed that these drastic changes are caused by excitation of large amplitude spin waves in the dot.