Calcium copper titanium oxide (CaCu 3 Ti 4 O 12 , abbreviated to CCTO) films were deposited on Pt/Ti/SiO 2 /Si substrates at room temperature (RT) by radiofrequency magnetron sputtering. As-deposited CCTO films were treated by rapid thermal annealing (RTA) at various temperatures and in various atmospheres. X-ray diffraction patterns and scanning electron microscope (SEM) images demonstrated that the crystalline structures and surface morphologies of CCTO thin films were sensitive to the annealing temperature and ambient atmosphere. Polycrystalline CCTO films could be obtained when the annealing temperature was 700°C in air, and the grain size increased significantly with annealing in O 2 . The 0.8-lm CCTO thin film that was deposited at RT for 2 h and then annealed at 700°C in O 2 exhibited a high dielectric constant (e¢) of 410, a dielectric loss (tan d) of 0.17 (at 10 kHz), and a leakage current density (J) of 1.28 9 10 -5 A/cm 2 (at 25 kV/cm).