Finite-element study of strain distribution in transistor with silicon–germanium source and drain regions

The strain field in the silicon channel of a metal–oxide–semiconductor transistor with silicon–germanium (Si_1-yGe_y) source and drain regions was evaluated using a finite-element method. The physical origin of the vertical and lateral strain components in the transistor channel region was explained. The magnitude and distribution of the strain components, and their dependence on device design parameters such as the spacing L between the Si_1-yGe_y stressors and the Ge mole fraction y in the stressors were investigated. Reducing the interstressor spacing L or increasing the Ge mole fraction y in the stressors increases the magnitude of the vertical tensile strain and the lateral compressive strain in the portion of the channel region where the inversion charge resides. This is beneficial for improving the hole mobility in p-channel metal–oxide–semiconductor transistors.