The formation of trench-gate power MOSFETs with a SiGe channel region
The fabrication of trench-gate power MOSFETs with a SiGe channel region has been proposed to further improve the device performance. A larger Ge mole fraction of Si1−xGex may cause a smaller on-state resistance but more degradation of the blocking voltage. A proper Ge mole fraction of 0.2 may be available, implementing a device with a blocking voltage of 30 V and a specific on-state resistance of about 0.70 Ω cm. On the other hand, a gradually changed Ge mole fraction of the Si1−xGex channel region may be employed to enhance the electric field in the channel region, and a specific on-state resistance of about 0.68 Ω cm can be achieved. Moreover, for this device with a SiGe channel region, a thin n-SiGe layer may be used in the drain near the channel region. This scheme can even yield a specific on-state resistance of only about 0.66 Ω cm which is 10% smaller than that caused by a conventional Si-channel device with the same process parameters.