In　order　to　enhance　the　breakdown　voltage　of　the　third-generation　SiGe　HBTs　for　microwave　power　application,　a　novel　design　methodology　of　HBTs　with　superjunction　structure　is　presented.　Both　the　superjunction　structure　location　and　the　concentration　is　optimized　step　by　step　to　compromise　the　breakdown　voltage　(BVCBO　and　BVCEO)　and　high　frequency　characteristics.　It　is　shown　that　the　superjunction　structure　located　inside　the　collector-base　space　charge　region　and　with　a　moderate　concentration　(as　well　as　twice　of　collector　concentration)　could　effectively　enhance　the　breakdown　voltage　with　less　expense　of　cutoff　frequency.　The　design　methodology　will　present　a　useful　guideline　of　SiGe　HBTs　for　microwave　power　application.