Contrary to recent claims, experimental results obtained in thin and thick Hafnium-based high-K gate dielectric stacks demonstrate that progressive breakdown is relevant in these insulators. For thin and thick stacks and both in NFETs and PFETs, the residual time distributions are found to be non-Weibull with two regions: a universally shallower slope at long times and a steeper slope at short times. The shallow distributions favour the coexistence of single-spot BD and multiple competing spots in different samples. Contrary to what happens in the case of SiON dielectrics, the final failure distribution is reported to be strongly dependent on the threshold current IF used to define device failure. Also contrary to what found for SiON single-layer dielectrics, the voltage acceleration and temperature activation energy of the residual time is reported to be much stronger than that of the first breakdown time. All these results emphasize the important role of progressive breakdown for high-K reliability assessment methodology. © 2011 IEEE.