A interconnect structure includes a substrate, a pair of interconnect pads, a pair of transmission lines. The outer conductor is made of an elongated tubular compartment having an elongated opening along one side of the compartment, and that the inner conductor is suspended within the tubular compartment by means of dielectric support means. In a hold mode of operation of the track-and-hold circuit, the switched capacitor circuitry is configured to couple the inputs of the second amplifier stage to the respective outputs of the first amplifier stage via the respective first and second capacitors. The Ge\u2014SiN bi-layer structure on the patterned sample is aniostropically etched so that an undercut is formed in the Ge layer, the SiN forming an overhang over a portion of the GaAs substrate.