A method provides a source-drain stressor for a semiconductor device including source and drain regions. Recesses are formed in the source and drain regions. An insulating layer covers the source and drain regions. The recesses extend through the insulating layer above the source and drain regions. An intimate mixture layer of materials A and B is provided. Portions of the intimate mixture layer are in the recesses. The portions of the intimate mixture layer have a height and a width. The height divided by the width is greater than three. A top surface of the portions of the intimate mixture layer in the recesses is free. The intimate mixture layer is reacted to form a reacted intimate mixture layer including a compound AxBy. The compound AxBy occupies less volume than a corresponding portion of the intimate mixture layer.