Calcium modified lead titanate thin films have been spin-coated on Pt/TiO2/SiO2/(100)Si substrates from sol-gel synthesized solutions containing a 10 mol% excess of PbO. Amorphous layers have been crystallized by a rapid thermal treatment at 650 degrees C for 50 a, using a heating rate of similar to 30 degrees C/s. Further thermal conditioning treatments were applied to the films, to study their effects on the ferroelectric response, by means of measurements of hysteresis loops, switching current curves, pyroelectricity, permittivity and leakage current densities. The origin of the leakages in these films is related with the nature of the electrode-ferroelectric interfaces. A mechanism based on the redistribution of charged defects after the thermal conditioning treatments is suggested. These treatments influence the trapping level and lead to the control of pinning of ferroelectric domains. This causes a direct effect on the switching process.