When forming cavities in active regions of semiconductor devices in order to incorporate a strain-inducing semiconductor material, an improved shape of the cavities may be achieved by using an amorphization process and a heat treatment so as to selectively modify the etch behavior of exposed portions of the active regions and to adjust the shape of the amorphous regions. In this manner, the basic configuration of the cavities may be adjusted with a high degree of flexibility. Consequently, the efficiency of the strain-inducing technique may be improved.