A new cell structure power MOSFET, which exhibits a lower on-state resistance and higher channel density than those with conventional layout geometry, is proposed. Vertical trench power MOSFETs are generally designed by either square or strip cell geometry; each has its own advantages and drawbacks. A new 'asymmetric wing cell' structure power MOSFET is proposed, fabricated and analysed. The on resistance of the proposed device can be further reduced. Both simulations and experiments show this structure has lower on resistance than the original design. It is also found that the avalanche characteristics of the proposed device are not sacrificed owing to the higher channel density.