A cleaning sequence usable in semiconductor manufacturing efficiently cleans semiconductor substrates while preventing chemical oxide formation thereon. The sequence includes the sequence of: 1) treating with an HF solution; 2) treating with pure H.sub.2SO.sub.4; 3) treating with an H.sub.2O.sub.2 solution; 4) a DI water rinse; and 5) treatment with an HCl solution. The pure H.sub.2SO.sub.4 solution may include an H.sub.2SO.sub.4 concentration of about ninety-eight percent (98%) or greater. After the HCl solution treatment, the cleaned surface may be a silicon surface that is free of a chemical oxide having a thickness of 5 angstroms or greater. The invention finds particular advantage in semiconductor devices that utilize multiple gate oxide thicknesses.