Silicon‐on‐insulator structures have been fabricated using implantation of 160 keV oxygen ions at a dose of 1.9×1018atoms/cm2with a wafer temperature of 500 °C and no oxide cap. Both the as‐implanted and annealed wafers were examined with optical reflectometry to determine the resultant interference pattern produced by the presence of the buried layer of SiO2. The optical data are compared to the predictions of a calculation which simulated the geometry using a detailed multilayer optical model. Parameters of the model were adjusted to provide a best fit to the data. The optical prediction closely matches data from destructive measurements. It is demonstrated that the redistribution of oxygen due to annealing can be monitored with this technique.