RF MEMS device packaging

A packaged RF MEMS device comprises a substrate 10 upon which is mounted an RF MEMS device 14; a cover 80 having a cavity to contain the device and an electrically conductive path 12' extending between the RF MEMS device and a peripheral surface of the packaged MEMS device. The cover and substrate define a cover-to-substrate interface 99 and a cover-to substrate interface boundary 97 within which track 12' extending from the device can terminate. A via 92 can extend between the track end and the peripheral surface of the package, through either the substrate or the wall structure (fig 16, 100). The cover can be transparent to allow inspection, formed from glass, and comprise a separate wall (fig 16, 98) spacing a lid 84 from the substrate. The wall may be glass or silicon oxide and frit bonded to the lid.