An electron spin resonance study has been carried out on the influence of isochronal annealing on the GeSi/SiO2 interfaces of the condensation grown (100)Si/SiO2/Ge0.75Si0.25/SiO2 structure. The thermal interface stability has been monitored in terms of the evolution of occurring paramagnetic interface defects, in particular, here involving the Ge dangling bond GePb1 point defect, previously identified as a detrimental interface trap. This reveals thermal post-growth interface degradation, initiating from annealing at the temperature similar to 440 degrees C onward, identified as substantial generation of GePb1 interface traps in addition to those naturally introduced into the system during sample manufacturing. In termsof GePb1 density, the interface thus appears only robust for thermal treatment in vacuum up to 440 degrees C. For T-an reaching similar to 520 degrees C, a drastic degradation occurs as exposed by an about two-fold increase in GePb1 density, which state is maintained up to T-an similar to 900 degrees C. Annealing in H-2 (similar to 1 atm) has a similar effect, exceptthat the interface degrades more gradually. Above 900 degrees C, the structure's integrity gradually collapsesbecause of disintegration (Ge escape) of the SiGe layer. As to device implementation, the data indicatethat temperatures of processing steps in O-deficient ambient should be kept below similar to 440 degrees C. (C) 2013 Elsevier B. V. All rights reserved.