A waveguide assembly integrated with a semiconductor wafer is provided. The waveguide assembly includes a waveguide channel defined by internal walls of the wafer lined with a metallic layer, and having at least one port for transmission of the RF signal into or out of the waveguide channel. The waveguide assembly also includes a semiconductor obstacle member disposed in the waveguide channel. The waveguide assembly may be fabricated using etching and deposition processes for semiconductor devices. In use, selectively varying either one or both of frequency or power level of electromagnetic radiation applied to the obstacle member varies electrical conductance of the obstacle member, and thereby varies the electrical impedance of the obstacle member to transmission of the RF signal through the waveguide channel. The waveguide assembly may be used for switching, attenuating, routing, filtering, and transforming the RF signal.