Abstract: To enhance the breakdown voltages (BV _CBO/BV _CEO) at a fixed cutoff frequency ( f _T) and current gain ( β), a model of npn SiGe heterojunction bipolar transistor (HBT) with superjunction collector was established by SILVACO TCAD. The research shows that the p-type superjunction layer inside the collector-base (CB) space charge region (SCR) lowers the electric field in the “dead space region”, and shifts the part of the high electric field somehow deep into the CB SCR which is located at the outside of the “dead space region”. As a result, impact ionization is suppressed, whereas the width of the CB SCR is slightly increased, and hence the breakdown voltages are improved at a minor expense of f _T and β. As the increase of the thickness of p-type superjunction layer ( d _p), the breakdown voltages including BV _CBO and BV _CEO are improved more obviously. However, d _p also needs to be optimized, considering that larger d _p would lead to Kirk effect and give rise to a dramatic decrease of f _T and β. Furthermore, the value of d _p in p-type superjunction layer is optimized as 0.2μm for a novel superjuction collector SiGe HBT with figure of merit of high frequency high voltage and high current ( f _T×BV _CEO× β). Compared with the conventional SiGe HBT, the figure of merit of f _T×BV _CEO× β for the novel device is markedly improved by 35.5%, which effectively develops the high voltage and high current application of power SiGe HBT.