A strain-induced layer is formed atop a MOS device in order to increase carrier mobility in the channel region. The dimension of the strain-induced layer in preferred embodiments may lead to an optimized drive current increase and improved drive current uniformity in an NMOS and PMOS device. An advantage of the preferred embodiments is that improved device performance is obtained without adding complex processing steps. A further advantage of the preferred embodiments is that the added processing steps can be readily integrated into a known CMOS process flow. Moreover, the creation of the photo masks defining the tensile and compressive strain-induced layers does not require extra design work on an existed design database.