The reliability of gate oxides is becoming a critical concern as oxide thickness is scaled below 4 nm in future technology. The breakdown detection algorithms in traditional reliability characterization techniques must be modified for sub-4 nm thick SiO² films that exhibit excessive tunneling currents and soft breakdown. It becomes essential to fully understand the physical mechanism(s) responsible for gate oxide wear-out and breakdown if reliability projections are based on the results of highly accelerated wafer-level GOI tests. Issues relating to the reliability testing of ultra-thin oxides are discussed with examples.