Abstract Bi 4− x La x Ti 3.0O 12 (BLT, x=0.67–0.70) ferroelectric thin films were prepared on a single crystalline aluminum oxide film onto Si substrate (c-Al 2O 3/Si), and amorphous phase aluminum oxide film onto Si substrates (a-Al 2O 3/Si) by the sol–gel method. In order for crystallization, the as-coated films were annealed at the temperature of 650 and 700 °C for 30 min. The crystalline quality, surface morphologies and electrical properties were affected by the substrate types as well as the annealing temperature. The BLT films annealed at above 650 °C exhibited typical bismuth layered perovskite structures with (00 l) preferred orientation. From X-ray diffraction analyses, the BLT films coated on c-Al 2O 3/Si substrate were higher in reflection peaks and smaller in full width at half maximum (FWHM) values compared with the ones coated on a-Al 2O 3/Si substrate. The R rms value of the film annealed at 700 °C on c-Al 2O 3/Si substrates was three times smaller than that of the film coated on a-Al 2O 3/Si substrate, showing a rather smooth surface when it was coated on c-Al 2O 3/Si substrate. The memory window voltage of the BLT film coated on c-Al 2O 3/Si substrate was 2.5 V, which is about twice compared with the one coated on a-Al 2O 3/Si substrate. The leakage current of BLT film annealed at 650 °C was approximately 1×10 −7 A/cm 2 at the applied voltage of 3 V for both samples.