In　this　paper,　high　on/off　capacitance　ratio　radio　frequency　micro-electro-mechanical-systems　(RF　MEMS)　switches　are　designed,　fabricated,　measured　and　analyzed.　Two　types　of　RF　MEMS　switches,　a　shunt　switch　with　a　contact　point　and　an　inline　switch　without　a　contact　point,　are　presented.　Metal-insulator-metal　(MIM)　fixed　capacitors　are　used　in　the　MEMS　switches.　The　electrode　topologies　of　RF　MEMS　switches　are　analyzed.　The　parameter　λ　is　defined　to　describe　the　relationship　between　the　capacitance　ratio,　the　height　of　the　beam　and　the　actuation　voltage.　The　measured　results　indicate　that,　for　MEMS　switch　#1　with　a　contact　point　and　gap　of　1　μm,　the　insertion　loss　is　better　than　0.64　dB　up　to　40　GHz,　and　the　isolation　is　more　than　20　dB　from　11.28　to　30.38　GHz　with　an　actuation　voltage　of　42　V.　For　the　inline　MEMS　with　a　displacement　of　1.5　μm,　the　insertion　loss　is　better　than　0.56　dB　up　to　40　GHz,　and　the　isolation　is　more　than　20　dB　from　4.45　to　30.48　GHz　with　an　actuation　voltage　of　36　V.　Circuit　models　and　measured　results　of　the　proposed　MEMS　switches　show　good　agreement.　From　the　fitted　results,　the　on/off　capacitance　ratio　is　∼227　for　the　MEMS　switch　#1　and　∼313　for　the　MEMS　switch　#2,　respectively.　Compared　with　traditional　MEMS　capacitive　switches　with　dielectric　material　Si3N4　and　a　relatively　lower　gap　(1.5　μm),　the　proposed　MEMS　switches　exhibit　high　on/off　capacitance　ratios.　©　2017　IOP　Publishing　Ltd.