This letter demonstrates a successful method for ON-state resistance reduction up to 20% by Shallow Trench Isolation (STI) fingers and with extra NLDD implant in the fingered region simultaneously for medium power devices. This fingered region provides a multidimensional electric field that avoids MOSFET breakdown voltage decrease, and it also shortens the drain-current conduction path. Therefore, low ON-state resistance and high drain driving current is obtained in our proposed device. Careful design for structural parameters of this STI finger is needed to achieve the optimum R ON performance without hurting breakdown voltage. ? 2009 IEEE.