AnewSOI(SiliconOnInsulator)highvoltagedevicewithStepUnmovableSurfaceCharges(SUSC)ofburiedoxidelayeranditsanalyticalbreakdownmodelareproposedinthepaper.Theunmovablechargesareimplementedintotheuppersurfaceofburiedoxidelayertoincreasetheverticalelectricfieldanduniformthelateralone.The2-DPoisson'sequationissolvedtodemonstratethemodulationeffectoftheimmobileinterfacechargesandanalyzetheelectricfieldandbreakdownvoltagewiththevariousgeometricparametersandstepnumbers.AnewRESURF(REduceSURfaceField)conditionoftheSOIdeviceconsideringtheinterfacechargesandburiedoxideisderivedtomaximizebreakdownvoltage.Theanalyticalresultsareingoodagreementwiththenumericalanalysisobtainedbythe2-DsemiconductordevicessimulatorMEDICI.Asaresult,an1200Vbreakdownvoltageisfirstlyobtainedin3μm-thicktopSilayer,2μm-thickburiedoxidelayerand70μum-lengthdriftregionusingalineardopingprofileofunmovableburiedoxidecharges.
