High-resolution and bright- and dark-field transmission electron microscopy are used to characterize and compare the interface structures and microstructure of PZT/RuO2/SiO2/Si and PZT/Pt/Ti/SiO2/Si ferroelectric thin films, with a view to understanding the improved fatigue characteristics of PZT thin films with RuO2 electrodes. The RuO2/PZT interface consists of a curved pseudoperiodic minimal surface. The interface is chemically sharp with virtually no intermixing of RuO2 and PZT, as evidenced by the atomic resolution images as well as energy dispersive x-ray analysis. A nanocrystalline pyrochlore phase Pb2ZrTiO7-x, x not equal 1, was found on the top surface of the PZT layer. The PZT/Pt/Ti/SiO2/Si thin film was well crystallized and showed sharp interfaces throughout. Possible reasons for the improved fatigue characteristics of PZT/RuO2/SiO2/Si thin films are discussed.