We fabricate epitaxial PbZr0.52Ti0.48O3/YBa2Cu3O7−x submicron film ferroelectric/superconductor heterostructures on the single-crystal YAlO3+1%Nd2O3 substrate by the pulsed laser deposition technique. Frequency independent low loss tan δ = 0.04 and dielectric constant of 950, high electric resistivity ρ (150 kV/cm)=6×1011Ω cm, remnant polarization of 32 μC/cm2, no visible fatigue after 107 short bipolar pulses switching indicate excellent electrical performance of the new capacitor structure. The slight crystallite polar axis misalignment and depolarizing effect were found to be responsible for the shape of the apparent polarization loop. The only fitting parameter depolarizing coefficient N = 2.37×10−4 gives the best fit between theory and experimental data and corresponds to prolate ellipsoidal shaped crystallites with the length-to-diameter ratio of 140. © 1998 American Institute of Physics.