A method for producing a SiGe stressor with high Ge concentration is provided. The method includes providing a semiconductor substrate with a source area, a drain area, and a channel in between; depositing the first SiGe film layer on the source area and/or the drain area; performing a low temperature thermal oxidation, e.g., a high water vapor pressure wet oxidation, to form an oxide layer at the top of the first SiGe layer and to form the second SiGe film layer with high Ge percentage at the bottom of the first SiGe film layer without Ge diffusion into the semiconductor substrate; performing a thermal diffusion to form the SiGe stressor from the second SiGe film layer, wherein the SiGe stressor provides uniaxial compressive strain on the channel; and removing the oxide layer. A Si cap layer can be deposited on the first SiGe film layer prior to performing oxidation.