In methods for smoothing or polishing a surface of a wafer, such as a silicon wafer, a liquid layer is formed on a surface of the wafer. The liquid layer may be an invisible microscopic layer, or a visible macroscopic layer. A flow of an oxidizing gas is directed over, against or onto the liquid layer of the surface of the wafer, in the presence of an etchant. The flow of gas thins the liquid layer at high points or areas on the surface of the wafer more than at low points or areas on the wafer surface. Consequently, the high points are oxidized and etched away more than the low points. As a result, the wafer surface is smoothed and polished.