In　order　to　enhance　the　breakdown　voltage　of　SiGe　HBTs　for　high　power　application,　the　model　of　NPN　SiGe　HBT　with　superjunction　collector　is　established　with　SILVACO　TCAD.　It　is　shown　that　the　superjunction　collector　with　iteratively　vertical　P　layers　and　N　layers　will　build　up　a　lateral　electric　field　to　change　the　distribution　of　the　electric　field,　reduce　the　peak　ionization　coefficient,　and　therefore　enhance　the　breakdown　voltage.　However,　the　thermal　effects　of　the　device　becomes　more　obviously　as　the　voltage　increases,　which　will　lead　to　the　thermal　instability　and　hence　limit　the　power　handling　capability　of　the　device.　Therefore,　the　layout　of　non-uniform　finger　spacing　is　further　designed　for　thermal　stability　improvement.　The　increasing　of　the　central　finger　spacing　could　effectively　suppress　the　heat　flow　from　adjacent　fingers　and　enhance　the　thermal　stability　of　novel　device　for　power　application.