In this paper, the authors present an experimental analysis on current conduction mechanisms in high-k oxides, where two metal–insulator–metal structures with different insulators (HfO2 and HfO2-x) are considered. Current density measurements indicate the existence of a perimeter-related component in the current, sizeable in HfO2, and negligible in HfO2-x samples, which have to be taken into account for a correct analysis of the device behavior and cannot be based only on the area scaling rules. For oxide breakdown, for example, a significant contribution of the perimeter-related current component results in conservative extrapolations of breakdown voltages for scaled devices.