A micro-electro-mechanical system varactor. The varactor includes a substrate, a lower bias conductor partially overlaying the substrate, a first signal conductor partially overlaying the substrate, a dielectric layer at least partially overlaying the first signal conductor, a support structure coupled to the substrate, and a flexible structure coupled to the support structure. The flexible structure is suspended over the substrate, includes an upper bias conductor overlaying at least part of the lower bias conductor and a top conductor overlaying at least part of the first signal conductor, configured to deflect in response to a bias voltage applied between the upper bias conductor and the lower bias conductor, and configured for separation between the top conductor and the dielectric layer by a varying separation distance dependent upon the bias voltage.