Strain engineering for electron mobility enhancement of strained Ge NMOSFET with SiGe alloy source/drain stressors

• The impact of channel width and length on the electron mobility of Ge strained NMOSFETs.
• New piezoresistance model is proposed for electron mobility stress response.
• Physical insights for scaling down post-Si CMOS devices in the future.

Stress distributions in a strained Ge NMOSFET with SiGe-alloy source/drain stressors and various lengths and widths are studied using 3D stress simulations in this work. Tensile stress along the transport direction is found to dominate the enhancement of electron mobility in devices with large widths. Stress along the vertical direction (perpendicular to the gate oxide) is found to affect the mobility the least, while stress along the width direction is enhanced at intermediate device widths. The impact of channel width and length scaling on the electron mobility gain is analyzed using the Kubo-Greenwood mobility formalism and the second-order piezoresistance model.

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