A crystalline (Na0.5K0.5) NbO3 (NKN) phase was formed for a film grown at 600 degrees C, but a K5.75Nb10.85O30 (KN) second phase was also observed in this film. Formation of the KN phase was due to the evaporation of Na2O. A homogeneous NKN phase was developed in the film grown at 300 degrees C and annealed at 800 degrees C under a Na2O atmosphere. This film exhibited the following good electric and dielectric properties: a high dielectric constant of 237.4 with a dissipation factor of 0.93% at 100 kHz, a low leakage current density of 1.0 x 10(-8) A/cm(2) at 0.1 MV/cm(2), and the high P-r and d(33) values of 21.1 mu C/cm(2) and 64.5 pm/V, respectively.