This thesis work addresses semiconductor device technology, characterization and modeling solutions that support the development of future generations of mobile phones, which are able to handle various wireless services in flexible manner. Today’s plurality of high data-rate communication signals requires high linearity and efficiency of the wireless transceiver. Currently handsets follow a multi-path implementation to integrate the various communication services. To handle the rapidly increasing complexity related to the growing number of communication standards, an adaptive RF front-end, able to change operating frequency, bandwidth, as well as output power, would be very advantageous. To reach this goal, new enabling tunable passive components are required that do not introduce any significant signal losses or signal quality degradation. In view of this, conventional varactor diodes disqualify themselves for linear RF applications due to their inherent non-linearity. In this thesis, novel varactor topologies in combination with specific doping profiles have been proposed that can overcome these limitations. Furthermore a dedicated double-sided contacting technology, namely silicon-on-glass, is introduced to manufacture these novel devices, which are subsequently characterized by newly developed dedicated methods. The usefulness of the proposed approach is demonstrated through several circuits, including adaptive matching networks, filters and phase shifters. Finally the linearity of silicon and gallium-arsenide bipolar transistors is investigated, exposing their fundamentally different linearity properties. Through careful characterization, not only the (dis)advantages of some technologies are highlighted, but also new directions and dedicated optimization techniques are provided to support the development of linear transmitters for future 3G/4G/LTE communication applications.