It　is　well　known　that　there　is　a　fundamental　tradeoff　among　the　breakdown　voltage　(including　BVCBO　and　BVceo),　the　cutoff　frequency　(fT),　and　the　current　gain　(β)　for　standard　collector　SiGe　HBTs.　In　order　to　enhance　the　breakdown　voltage　at　a　fixed　fT　and　β,　the　superjunction　collector　design　is　proposed　and　the　model　of　NPN　SiGe　HBT　with　a　superjunction　P-type　doping　layer　inside　the　collector-base　(CB)　space　charge　region　(SCR)　is　established　with　SILVACO　TCAD.　It　is　shown　that　the　inserted　P-type　layer　provides　a　reverse　electric　field　to　change　electric　field　distribution,　reduce　the　peak　ionization　coefficient,　and　hence　enhance　the　breakdown　voltage　with　a　slight　decrease　off　and　β.　Furthermore,　a　novel　composite　of　double　P-type　layers　inside　the　CB　SCR　is　proposed　for　further　improvement　of　the　breakdown　voltage　at　a　minor　expense　of　fT　and　β　It　is　shown　that　SiGe　HBT　with　double　P-type　layers　has　the　lowest　peak　electric　field,　the　lowest　peak　ionization　coefficient　and　consequently　the　highest　breakdown　voltage　when　compared　with　standard　collector　and　one　P-type　layer　collector　SiGe　HBTs.　As　a　result,　the　figure　of　merit　fT×BVCEO×β　is　improved　from　65945GHz-V　to　83729GHz-V,　which　effectively　develops　the　high　frequency　and　high　power　application　of　SiGe　HBTs.　©　2015　IEEE.