Abstract: Semiconductor substrate materials, such as silicon, useful in the manufacture of electronic devices, such as integrated circuits, having a 0.05 to 2.0 micron thick layer of polysilicon on the backside to improve gettering capabilities of defects, contaminants and impurities away from the active device region of the substrate are provided with a 10 to 40 micron deep region from the surface having reduced oxygen concentration. The oxygen denuding is accomplished by heating the substrate material at a temperature of 1050.degree. to 1250.degree. C. first in the presence of oxygen to break up oxygen nuclei, secondly in the presence of oxygen and halogen to permit stacking fault retrogrowth and oxygen outdiffusion, and thirdly in the presence of oxygen, nitrogen and/or argon.