Fabrication of high performance thin-film RF-MEMS structures directly on surface treated LTCC substrates has been investigated and demonstrated. After extensive testing of different LTCC materials as well as the characterization of lapping and polishing conditions, Heraeus CT707 was chosen as substrate material. The fabrication process for high performance thin film patterning and RF-MEMS structures has been developed, optimised and demonstrated. The release process for RF-MEMS structures has been optimised taking also into account the compatibility with LTCC materials. Also, hermetic sealing for the MEMS structures using brazing both with Kovar and ceramic lids has been designed, optimised and demonstrated.