The SrTiO3ultrathin film capacitors were realized on Nb‐doped single‐crystal SrTiO3substrates by chemical vapor deposition. The leakage current density of 10.4 nm thick SrTiO3thin‐film capacitor was below 1×10−8A/cm2in the applied voltage range of −1.8 to +0.45 V, and its SiO2equivalent thickness was 0.48 nm. The relative dielectric constant was over 160 for SrTiO3thickness above 20 nm, but it decreased for SrTiO3thickness below 20 nm. Dependence of leakage current on SrTiO3film thickness was slight. These results could be explained by the existence of applied electric field concentration near the SrTiO3/electrode interface. ©1995 American Institute of Physics.