Abstract: A method to control the quality of a buried oxide region, and to substantially reduce or eliminate deep divots in SOI substrates is provided. Specifically, the inventive method includes the steps of implanting oxygen ions into a surface of a Si-containing substrate; and annealing the Si-containing substrate containing the implanted oxygen ion at a temperature of about 1300° C. or above and in a chlorine-containing ambient so as to form a buried oxide region that electrically isolates a superficial Si-containing layer from a bottom Si-containing layer. The chlorine-containing ambient employed in the annealing step includes oxygen and a chlorine-containing carrier gas such as HCl, methylene chloride, trichloroethylene and trans 1,2-dichloroethane.