We, for the first time, demonstrate a new process for Si power transistor manufacturing. The new process, combining the HMIC process and flip-chip process, completely changes the Si power transistor internal matching circuits design and manufacturing. S-band Si power transistor was used as a testing vehicle and under pulse operation condition Pout=23 W with 7.9 dB of gain a n d 3 9 % of e f f i c i e n c y w e r e o b t a i n e d a t f=3.05GHz and Vcc=36V.