An Ultra-Fast On-The-Fly (UF-OTF) IDLIN technique having 1 μs resolution is developed and used to study gate insulator process dependence of NBTI in Silicon Oxynitride (SiON) p-MOSFETs. The Nitrogen density at the Si-SiON interface and the thickness of SiON layer are shown to impact temperature, time, and field dependencies of NBTI. The plausible material dependence of NBTI physical mechanism is explored. © 2007 IEEE.