The microstructure and leakage current of lead zirconate titanate (PZT) thin films were investigated to understand the mechanism of the leakage current and also to attempt to improve the leakage characteristics. The PZT thin films were prepared using a sol-gel process followed by crystallization in three different gas ambients, i.e. N-2, air and O-2 The three kinds of crystallized samples show different microstructure and orientation. Electrical characterization of the PZT thin films including the permittivity, P-E hysteresis, and the leakage current was carried out. It was found that the leakage current was affected not only by the microstructures of the films but also by the interface between the Pt electrode and the PZT film. Moreover, it was found that more than one conduction mechanism is involved in the range of electric field used in the experiment. In the low electric field region the current conduction is ohmic and its mechanism is found to be electron hopping among electron traps. In the high field region the sample treated in N-2 shows Schottky emission, the sample treated in O-2 shows space charge limited conduction, and the sample treated in air shows both Schottky and space charge conduction together.