A　1200V　vertical　variable　doped　semi-super　junction　fast　recovery　diode　(VVD-Semi-SJ-FRD)　is　presented　in　this　paper.　In　super　junction　structure,　P-pillar　and　drift　region　are　needed　to　maintain　charge　balance.　As　a　result,　the　reverse　breakdown　voltage　of　the　semi-super　junction　fast　recovery　diode　is　very　sensitive　to　the　doping　concentration　of　P-pillar,　resulting　in　a　narrow　process　window　for　ion　implantation　of　P-pillar.　The　structure　proposed　in　this　paper　uses　three　epitaxial　layers,　the　epitaxial　layer　near　the　side　of　the　P-type　region　and　the　epitaxial　layer　below　the　P-pillar　is　low-doping,　and　the　middle　is　high-doping.　By　analyzing　the　influence　of　P-pillar　concentration　on　reverse　breakdown　voltage　and　the　electric　field　distribution　at　different　concentrations,　it　is　shown　that　the　proposed　structure　can　effectively　reduce　the　sensitivity　of　reverse　breakdown　voltage　to　P-pillar　doping　concentration,　thus　enlarges　the　process　window　of　P-pillar　ion　implantation.　©　2022　Association　for　Computing　Machinery.