We propose a novel technique of oxidizing silicon cantilever tips to characterize silicon-based semiconductors by tip-enhanced Raman measurements. The technique uses thermal oxidization process under steam atmosphere. It is aimed for the suppression of Raman scattering originating from the silicon tip itself without degrading the tip sharpness. The thickness of the oxidized silicon on the silicon tip is controlled by the thermal oxidization time. We successfully obtained 250-nm thick silicon dioxide in 1100 degrees C temperature under steam at 10-min oxidization time. Using the oxidized tip, we experimentally verified that silicon Raman vibration was completely suppressed.