Since high-k materials are very different from SiO2, both structurally and electrically, conventional characterization and reliability methods that have been developed for SiO2 devices may not be applicable to high-k dielectric devices. Fast transient charging effects degrade the drive current of high-k devices due to electron trapping in the gate dielectric. Because of this phenomenon, conventional DC drain current-gate voltage (I-d-V-g) measurements may underestimate the drain current, which translates to lower extracted mobility values, which has been confirmed by ultra short pulse measurements. The fast spontaneous post-stress relaxation phenomenon could complicate the assessment and interpretation of the threshold voltage (V-TH) instability in high-k devices. The results obtained with a novel inversion pulse measurement method demonstrate that the V-D, relaxes after a post-stress period of a couple of hundred microseconds. Consequently, the magnitude of V-TH instability is underestimated when a relatively slow switching matrix is used for the stress/sense measurements. (c) 2005 Elsevier B.V All rights reserved.