Some embodiments of the present disclosure relates to a method and a device to achieve a strained channel. A volume of a source or drain recess is controlled by a performing an etch of a substrate to produce a recess. An anisotropic etch stop layer is then formed by doping a bottom surface of the recess with a boron-containing dopant, which distorts the crystalline structure of the bottom surface. An anisotropic etch of the recess is then performed. The anisotropic etch stop layer resists anisotropic etching such that the recess comprises a substantially flat bottom surface after the anisotropic etch. The source or drain recess is then filled with a stress-inducing material to produce a strained channel.