Featured　Application　The　split　gate　resurf　stepped　oxide　with　highly　doped　epitaxial　layer　(HDSGRSO)　UMOSFET　has　extremely　low　on-state　resistance,　therefore,　it　can　be　used　in　synchronous　rectification　circuits　to　replace　rectifier　diodes　to　reduce　rectification　losses.　It　can　greatly　improve　the　efficiency　of　the　DC/DC　converter　and　there　is　no　deadtime　voltage　caused　by　the　Schottky　barrier　voltage.　On　the　other　hand,　it　can　be　applied　to　the　high　frequency　switching　due　to　its　excellent　dynamic　characteristics.　The　split　gate　resurf　stepped　oxide　with　highly　doped　epitaxial　layer　(HDSGRSO)　UMOSFET　has　been　proposed.　The　epitaxial　layer　of　HDSGRSO　u-shape　metal　oxide　semiconductor　field　effect　transistor　(UMOSFET)　has　been　divided　into　three　parts:　the　upper　epitaxial　layer,　the　lower　epitaxial　layer　and　the　middle　epitaxial　layer　with　higher　doping　concentration.　The　research　shows　that　the　reduced　SURface　field　(RESURF)　active　has　been　enhanced　due　to　the　high　doped　epitaxial　layer,　which　can　modulate　the　electric　field　distribution　and　reduce　the　internal　high　electric　field.　Therefore,　the　HDGRSO　UMOSFET　has　a　higher　breakdown　voltage　(BV),　a　lower　on-state　specific　resistance　(R-SP)　and　a　better　figure　of　merit　(FOM).　According　to　the　results　of　Technology　Computer　Aided　Design　(TCAD)　simulations,　the　FOM　(BV2/R-SP)　of　HDSGRSO　UMOSFET　has　been　improved　by　464%,　and　FOM　(R-SP　x　Q(gd))　of　HDSGRSO　UMOSFET　has　been　reduced　by　27.9%　compared　to　the　conventional　structure,　respectively,　when　the　BV　is　240　V.　Furthermore,　there　is　no　extra　special　process　required　in　this　advanced　fabrication　procedure,　which　is　relatively　cost-effective　and　achievable.