An electron spin resonance study has been carried out on the effect of in situ applied in-plane stress to (111)Si substrates during oxidation on the formation of inherent P-b (Si(3)equivalent toSi(.); Si dangling bond) interface defects in (111)Si/ SiO2. Analysis for various, both compressive and tensile, stress levels reveals the properties of these electrically active point defects to be significantly affected, in particular their incorporated inherent density and signal shape. Interestingly, the inherent P-b density is reduced by applied tensile stress, with an opposite result for compressive. The data support the commonly accepted relationship between inherent incorporation of the P-b defects and Si/SiO2 interface mismatch. (C) 2004 Elsevier B.V. All rights reserved.