We have prepared YBa 2 Cu 3 O 7 thin superconducting films on (11[macr ]02) Al 2 O 3 substrate with CeO 2 buffer layer using an aerosol MOCVD process. Texture analysis using X-ray diffraction showed a high degree of epitaxial character of both YBa 2 Cu 3 O 7 and CeO 2 films. Study of the microstructure of the YBa 2 Cu 3 O 7 layer and YBa 2 Cu 3 O 7 /CeO 2 and CeO 2 /Al 2 O 3 interfaces by transmission electron microscopy revealed relaxation of the CeO 2 and YBa 2 Cu 3 O 7 layers. The films exhibited a critical temperature T c ((R=0))=84-88 K, resistivity at room temperature of 600 [mu ][Omega ] cm, a resistivity ratio [rho ] ( 3 0 0 K ) /[rho ] ( 1 0 0 K ) higher than 3 and critical current density up to 3 [times ] 10 9 A cm [ m i n u s ] 2 at T=77 K.