The experimental conditions which render the exact stoichiometry of PZT(52/48) thin films deposited on Pt thin film on Si(100) by reactive cosputtering have been investigated. As-deposited PZT is amorphous containing α-PbO2 microcrystallites. As annealing temperature increases, the amorphous PZT films crystallize into pyrochlore and perovskite with pseudo-cubic structure in sequence. The perovskite PZT annealed above 750 °C evolves into a phase of morphotropic phase boundary. In the perovskite PZT thin films, the leakage current increases with annealing time. Also, the dielectric constant increases with film thickness and annealing temperature, which is discussed in conjunction with PZT/Pt interfacial morphology.