The Plessey GaAs Foundry Process is based on proven, reliable technology with the greatest emphasis placed on manufacturability, reproducibility and yield. Since the introduction of commercial processes in 1985, Plessey has maintained a policy of enhancement and updating rather than replacement as new processes become available. For example, usable frequency limits have been pushed from 12GHz to 14GHz and now to 20GHz with 0.5μm technology and via holes. This policy will continue in the future. Advanced processes have been developed, for example, for the generation of many watts of mean power from a MMIC. A HEMT has also been demonstrated and this will form the core technology for the forthcoming Plessey F40 process which will operate at 40GHz.