Simulation and optimization of strained Si1-xGex buried channel p-MOSFETs

Deep submicron (0.35 mu m) strained Si1-xGex buried channel p-MOSFETs with a Ge concentration up to 50% were simulated using the MEDICI device simulator. A buried channel structure offers several benefits over a surface channel structure without a Si cap. Simulation results show that the maximum drain current increases monotonically with the Ge mole fraction. The drive current enhancement is more than 300% for Si-0.5 Ge-0.5 over Si. Subthreshold characteristics were analyzed for different Ge mole fractions in this study. The effects of Si cap layer thickness and Si1-xGex channel thickness on drive current and gate voltage operating window were analyzed. The simulation results show that the drive current is the highest when the Si1-xGex layer thickness is between 100 and 300 Angstrom and that Si1-xGex layer thickness can be as low as 50 Angstrom with less than 10% penalty in the drive current, For structures with a 50 Angstrom Si cap layer. (C) 2000 Elsevier Science Ltd. All rights reserved.