Epitaxial lead zirconate titanate thin films were grown by pulsed laser deposition method on LaAlO3 substrate using La0.5Sr0.5CoO3 (LSCO) as the bottom electrode. Two different top electrode systems were studied: a single platinum layer and a platinum/LSCO bi-layer. The as-grown, post-annealed and fatigued samples were subsequently investigated via polarization-electric field hysteresis loops measurement and deep level transient spectroscopy. It was found that polarization fatigue occurs only for films with single platinum layer top electrode but not with Pt/LSCO electrode bi-layer ones. Hole traps with activation energy 0.209 eV were detected in the fatigued samples with single Platinum top electrode. This is the first observation of fatigue-related deep levels in PZT films and provides new insight into the switching fatigue mechanisms. (C) 2003 Elsevier B.V. All rights reserved.