We have studied the correlations between deposition parameters and structural and electrical properties of YBa2Cu3O7−&dgr;thin films growninsituby sequential ion beam sputtering. Epitaxial,c‐axis oriented YBa2Cu3O7−&dgr;films were grown both on (100) SrTiO3and on (100) MgO substrates following the stacking sequence of the ‘‘123’’ compound, with deposited layer thicknesses nominally equal to 1 monolayer. Thec‐axis lattice parameters obtained were larger than the corresponding lattice parameter in bulk samples, even after low‐temperature anneals in O2. The transition temperatures were found to decrease with the enlargement of thec‐axis lattice parameter. A clear correlation between growth temperature and the value of thec‐axis lattice parameter was observed. Thec‐axis lattice parameter and the x‐ray linewidth of Bragg reflections with theGvector along thec‐axis were also found to be correlated. This suggests a relationship between thec‐axis lattice parameter and the structural coherence of the epitaxial films.