The work is related to an Agile Filter which is a specific RF block to be inserted between an antenna and a first stage of pre-amplification in future on board antenna systems or any future multi-purpose communications terminals. It will be able to process signals in the frequency range between 2 and 18 GHz with target insertion loss below 3dB. The basic idea of the demonstrator studied and developed in this project is to evaluate a SiP approach combining heterogeneous technologies and 3D integration and packaging. This paper presents the process flow used to design, fabricate and integrate in 3D a tunable RF filter which tunability is obtained by the use of MEMS varactors based on a copper on glass technology and stacked on micro-PCD for the electronic control functions. MEMS+ parameterized structures for RF MEMS varactor designs are presented with dimension constraints to be compatible with the space available at the end of each combline sub-filter. Indeed, the MEMS capacitors are composed of a mobile square membrane of 210μm by side and overall size of 600μm. In addition, these RF MEMS tunable capacitor models were automatically transferred into VerilogA for rapid system-level simulation usable further in ADS environment to verify the RF performances.