Molecular beam epitaxy of silicon on substrates with patterned oxide overlayers results in single-crystalline films in the oxide windows (differential Si-MBE). A concept for fabrication of monolithically integrated circuits using differential Si-MBE is given. We report about properties of differential Si-MBE films grown at temperatures between 550 and 750 degree C. Integrated bipolar transistors in differential Si-MBE films were fabricated and characterized. Transit frequencies up to 5 GHz could be realized with this design.