Negative bias temperature instability (NBTI) is a well-known reliability concern for PMOS
transistors. We review the literature to find seven key experimental features of NBTI
degradation. These features appear mutually inconsistent and have often defied easy
interpretation. By reformulating the Reaction–Diffusion model in a particularly simple form,
we show that these seven apparently contradictory features of NBTI actually reflect different
facets of the same underlying physical mechanism.