The present invention relates to a method of treating wafers comprising at least one surface layer of silicon-germanium (SiGe) and a layer of strained silicon (sSi) in contact with the SiGe layer, the sSi layer being exposed by etching of the SiGe layer, the method comprising the steps of: (a) a first selective etch of the SiGe layer, optionally followed by an oxidative cleaning step; (b) a rinsing step using deionized water; (c) drying; and (d) a second selective etch step. The present invention relates to a wafer comprising at least one surface layer of strained silicon (sSi), the at least one surface layer of sSi having a thickness of at least 5 nm and at most 100 μm and having at most 200 defects per wafer.