We report high‐resolution transmission electron microscopy and electron diffraction studies of the heteroepitaxial superconductor‐insulator‐superconductor system YBa2Cu3O7−x‐SrTiO3‐YBa2Cu3O7−xdeposited on polished (001)MgO substrates byinsitulaser ablation. The resulting films grow epitaxially and consistently preserve a parallel orientation between the close‐packed (001)YBa2Cu3O7−xplanes and (001)SrTiO3planes over the entire trilayer, even in the presence of ledges or steps along vicinal interfaces. Although the interface regions showed strain occasionally relieved by stacking faults, they were free of disorder and any evidence of impurity phases. The observed epitaxial growth is very likely responsible for the excellent electrical properties found in similarly constructed multilayer interconnects.