We use a plan-view transmission electron microscope technique to unambiguously image the “physical” interface position between Si and furnace grownSiO2layers. As-grown ∼6-nm-thick (100) oxides have a very high roughness (&sgr;∼10–15 Å), which can be removed by short annealing in an inert gas at a growth temperature of 900 °C. ©1997 American Institute of Physics.