A 7-mask self-aligned SiGe base bipolar transistor has been newly developed. This transistor offers several advancements to a super self-aligned selectively grown SiGe base (SSSB) transistor which has a selectively grown SiGe-base layer formed by a cold-wall ultra high vacuum (UHV)/CVD system. The advancements are as follows: (1) a BPSG-filled arbitrarywidth trench isolation on a SOI is formed by a high-uniformity CMP with a hydro-chuck for reducing the number of isolation fabrication steps, (2) polysilicon-plug emitter and collector electrodes are made simultaneously using an in-situ phosphorusdoped polysilicon film to decrease the distance between emitter and collector electrodes and also to reduce the fabrication steps of the elecrodes, (3) a n+-buried collector layer is made by a high-energy phosphorus ion-implantation technique to eliminate collector epitaxial growth, and (4) a germanium profile in the neutral base region is optimized to increase the fT value without increasing leakage current at the base-cellector junction. In the developed transistor, a high performance of 80-GHz fT and mask-steps reduction are simultaneously achieved.