The ageing behaviour of epitaxial YBa2Cu3O7 (YBCO) films an Si (100) with CeO2/YSZ buffer layers is studied. For the YBCO/CeO2/YSZ/Si system, its ageing is weaker than the YBCO/YSZ/Si system. The experimental critical thickness of YBCO films for YBCO/CeO2/YSZ/Si systems is only 40 nm, otherwise cracks appear in the film. The formation of cracks is analyzed by means of fracture mechanics theory. The estimated thermal stress and elastic strain in crack-free YBCO layers reach 2.41 GPa and 1.5% at 77 K, respectively. Depositing another non-superconducting YBCO (YBCO*) film an top of YBCO as a passivation layer makes the critical thickness increase up to 70 nm. These films cannot bear surface etching and tempering temperatures higher than 110 degrees C in lithography.