A parallel beam reflection technique has been developed in our laboratory for measuring intrinsic residual stress for Si wafers thermally oxidized at temperatures of 600–1150 °C. A detailed description of this technique is provided, and stress values calculated for thermally grown SiO2films on Si are consistent with those reported in the literature. Low temperature thermal oxidations resulted in compressive intrinsic SiO2stresses greater than 4×109dyn/cm2.