Vertical Power ${\rm H}k$-MOSFET of Hexagonal Layout

A vertical power MOSFET with hexagonal cells by using high-k (Hk) insulator (Hk-MOSFET) in voltage-sustaining region is studied. Both cases of the Hk-MOSFET hexagonal cell, one with a semiconductor in the center of each hexagonal cell and another with an insulator in the center, are discussed. The optimized specific on-resistance (R
_sp
) of an Hk-MOSFET for the former case is around 20% smaller than that of using an interdigitated layout. For the latter case, the optimizedRsp is further reduced. The theoretical predictions are in good agreement with the numerical results from simulation. An example indicates that the R
_sp
of a hexagonal Hk-MOSFET for the latter case is nearly two-thirds that of an interdigitated one, and is almost identical to that of an optimized superjunction (SJ) MOSFET with a hexagonal cell under the same breakdown voltage (V
_B
). The V
_B
of an Hk device is more robust than that of an SJ device to the charge imbalance effect. Although Hk-MOSFET has a little slower transient response than that of SJ-MOSFET, the body diode reverse recovery behavior is much softer than the latter.