A process for cleaning a silicon surface. First, a silicon surface is cleaned with an oxidant solution. Next, the silicon surface is rinsed with HF vapor or liquid and then with the silicon surface with hydrogen water or deionized water under megasonic agitation. Finally, the silicon surface is cleaned with an oxidant solution a second time. The present inventive cleaning process can be applied in thin film transistor (TFT) fabrication and the TFT obtained has higher electron mobility.