For the first time it was possible to obtain a current gain increase to more than 0 dB at frequencies beyond the transit frequency f(T) by use of an SiGe resonance phase transistor (RPT). This was achieved by using a very thick base layer with a graded high content Ge profile and a thick low doped collector to get a large phase delay in the carrier drift and a delayed injection. Based on these ideas the so called RTP was fabricated. To get sufficient phase delay in the base, it is necessary to grow very thick base layers (w(B)) With graded Ge content (x) up to high Ge concentrations (i.e. w(B) = 120 nm, chi = 5-30%). These structures were grown by MBE at low temperatures in the ultrametastable growth regime. The manufacturing of the transistors was performed by a low temperature process with temperatures below 450 degreesC, using a NiSi/Ag contact metallisation. (C) 2004 Elsevier Ltd. All rights reserved.