Amorphous Bi-Fe-O x films prepared on SrTi0 3 (100) substrates using a conventional r.f. magnetron sputtering system were crystallized by post-annealing at 873 K in an atmosphere. Microstructural observations by X-ray diffraction and cross-sectional transmission electron microscopy revealed that the crystallized Bi-Fe-O x films were well-epitaxially BiFe0 3 fabricated without interfacial layer although as-prepared film was amorphous structure with excess Bi. The crystallized BiFe0 3 films have fairly epitaxial compatibly ([001](001)BiFe0 3 // [001](001)SrTiO 3 ). These results indicate that (1) BiFe0 3 has good epitaxial compatibility with SrTi0 3 and (2) crystallizing amorphous Bi-Fe-O x is one possible method that can be used to fabricate high-quality multiferroic barriers for tunnel junctions.