Lead zirconate titanate PbZr0.50Ti0.50O3 (PZT) ferroelectric thin films were successfully deposited on Pt(1 1 1)/Ti/ SiO2/Si substrates by a modified sol-gel method using zirconium nitrate as a substitute for the conventional zirconium alkoxide. The precursor solutions were hydrolyzed with different H2O/Pb ratios. The effect of hydrolysis ratios of the solution on the microstructure for the PZT thin films were investigated via X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques. The XRD results show that the PZT films exhibit (1 1 1)-orientation and the degree of the (1 1 1)-orientation decreases with the increase of hydrolysis ratio. These results indicate that the ferroelectric behavior can be improved by an appropriate choice of H2O/Pb ratio.