Provided is a method of preparing a dielectric film having a nanoscale three-dimensional shape and including an oxide, the oxide represented by RAMBOC where R is a divalent element and M is a pentavalent element, the method may include synthesizing a target material, the target material including the divalent element and the pentavalent element; and forming the oxide by depositing the divalent element and the pentavalent element, from the target material, onto a substrate such that the oxide includes a perovskite-type crystal structure, 1.3