RF-MEMS represent a feasible solution to obtain very low power dissipation and insertion loss, very high isolation and linearity switch respect to “solid state” technologies. In this paper we demonstrate the possibility to fully integrate the process fabrication of RF-MEMS switches in the GaN-HEMT manufacturing steps to develop a RF-MEMS/MMIC prototype. MEMS RF performance reveals an insertion loss and an isolation respectively better than 0.6 dB and 25 dB in the frequency range 5-50 GHz. Moreover the coexisting HEMT devices show a fmax=40 GHz and 6.5 W/mm density power, demonstrating the integration achievability.