High quality ĉ-axis oriented thin and ultra-thin films have been grown in situ on (100) surfaces of ZrO2, SrTiO3 and MgO. Sharp transitions were observed with Tc,zero of 87–91 K for films thicker than 70 Å. On atomically polished MgO substrates films as thin as 15 Å revealed a full transition to superconductivity above 45.5 K. The critical current density at 77 K was found to be strongly dependent on film thickness. A maximum value was found for a 100 Å film with 8 × 106A/cm2 at 77 K. Also, YBCO/PBCO/YBCO multilayer thin films have been fabricated in situ by the same technique. The epitaxy is maintained throughout the whole multilayer system. The superconducting properties of YBa2Cu3Ox layers do not change compared to single layers. Interdiffusion and possible chemical reaction close to the interfaces can be neglected.