7.1. Introduction7.2. Leakage current in metal/insulator/metal structures7.2.1. Metal/insulator contact: definitions7.2.1.1. Fermi level, work function, and electron affinity7.2.1.2. Neutral contact7.2.1.3. Blocking contact7.2.1.4. Ohmic contact7.2.1.5. Intrinsic and extrinsic carriers7.2.2. Conduction mechanisms limited by the interfaces7.2.2.1. Schottky emission7.2.2.2. Tunneling conduction7.2.3. Conduction mechanisms limited by the bulk of film7.2.3.1. Poole-Frenkel emission7.2.3.2. Hopping conduction7.2.3.3. Conduction limited by the space charge7.3. Problem of leakage current measurement7.3.1. Relaxation current and true leakage current7.3.1.1. Staircase procedure7.3.1.2. Pulse procedure7.3.2. Drift of true leakage current7.3.3. Discussion7.4. Characterization of the relaxation current7.4.1. Origin of the relaxation current7.4.2. Modeling of relaxation currents7.4.2.1. Temperature evolution7.4.2.2. Voltage evolution7.4.3. Conclusion7.5. Literature review of true leakage current in PZT7.6. Dynamic characterization of true leakage current: I(t, T)7.6.1. Study of the resistance degradation7.6.1.1. State of the art7.6.1.1.1. Role of oxygen vacancies7.6.1.1.2. Role of the interfaces7.6.1.2. Modeling of the resistance degradation7.6.1.3. Temperature activation of the resistance degradation7.6.1.4. Influence of voltage on resistance degradation7.6.1.5. Discussion – interpretation of results7.6.1.5.1. Influence of polarity: roles of bulk and interfaces7.6.1.5.2. Capacitive measurements before and after degradation7.6.1.5.3. Reversibility of the resistance degradation mechanism7.6.1.6. Conclusion7.6.2. Study of the resistance restoration phenomenon7.6.2.1. Modeling the resistance restoration7.6.2.2. Temperature activation of resistance restoration7.6.2.3. Influence of voltage on the resistance restoration7.6.3. Conclusion7.7. Static characterization of the true leakage current: I(V,T)7.7.1. Space-charge influenced-injection model7.7.2. Quantitative description of the model7.7.2.1. Ohmic regime7.7.2.2. Static Schottky regime7.7.2.3. Dynamic Schottky regime7.7.3. Static modeling Jmin(V) and Jmax(V)7.7.3.1. Experimental procedure7.7.3.2. Modeling results7.7.3.3. Discussion: consistency of the model7.7.3.4. Temperature modeling of Jmax(V)7.8. Conclusion7.9. Bibliography