Effects of extended poly gate on the performance of strained P-type metal-oxide-semiconductor field-effect transistors with a narrow channel width

The layout patterns of nano-scale devices have significant impacts on device performance when an increase in operating velocity is considered. Thus, advanced strain engineering of metal-oxide-semiconductor field-effect transistors (MOSFETs) is necessary when highly scaled gate lengths are employed. The foregoing mechanical effects are observable when a device with a narrow channel width is utilized. However, when a device integrated with an extended poly gate is scaled down to several hundreds of nanometers, the induced stress contours of the channel region and corresponding mobility gain become troublesome and must be resolved. This study investigates the mechanical impacts of extended gate widths on the mobility gains of p-type MOSFETs. The selected MOSFET has a SiGe stressor embedded in its source and drain regions, as well as a compressive contact etch stop layer. Three-dimensional finite element simulation is performed to emulate the stress contour within the Si channel and estimate the related mobility gain. Sensitivity analyses of the simulation results using factorial designs and response surface methodology indicate that stresses within the Si channel are induced by a bending force determined by the extension of the poly width. A significant enhancement in mobility gain is found when an extended poly width combined with proper arrangements of the device geometry is applied.