A method whereby perovskite type oxide dielectric thin films with ABO.sub.3 structure are able to be formed with such features as good stability, uniformity, reproducibility, or the like, with high through-put by having a deposition process, wherein the thin films are deposited on a substrate, and a stabilization process, where no deposition of the thin films takes place, repeated alternatingly while the substrate temperature being kept near the temperature at which perovskite type oxide dielectric thin films are formed. Also, by employing (i) a processing method wherein a decomposing excitation of a reactive gas due to plasma takes place on or near the deposition surface in a gaseous atmosphere comprising a gas that reacts with the elements composing the thin films, (ii) a processing method wherein an oxidation reaction takes place on the deposition surface in a gaseous atmosphere comprising at least ozone (O.sub.3), and (iii) a processing method wherein light of short wave length is irradiated on the deposition surface in a gaseous atmosphere comprising at least reactive elements in the non-deposition process, the oxygen concentration in the deposited thin films is adjusted and dielectric thin films of good quality and an extremely low defect content are realized.