Transitions regions at Si-SiO2 interfaces contain excess suboxide bonding arrangements which contribute to interface roughness and also can give rise to electronically active defects. This article provides insights into the origin and temperature stability of these suboxide bonding arrangements by studying different interface formation processes, e.g., rapid thermal oxidation and plasma-assisted oxidation, and then subjecting these interfaces to rapid thermal annealing (RTA). The interfacial bonding chemistry has been studied before and after the RTA by Auger electron spectroscopy and it has been demonstrated that interfacial transition regions with suboxide bonding are a direct result of thermal and plasma-assisted oxidation at temperatures up to at least 800 degrees C, and that the excess suboxide bonding in interfacial transition regions is significantly reduced following a 30 s, 900 degrees C RTA. The kinetics of this interfacial annealing process are essentially the same as observed for the RTA-induced separation of homogeneous suboxide thin films (SiOx, x<2) into silicon nanocrystals and stoichiometric SiO2.