The work described here uses microfabrication methods to integrate semiconductor devices with micromachined waveguide cavities to form submillimetre-wave frequency multipliers. Processing schemes involve both planar and three-dimensional lithography, using conventional photoresist and epoxy based SU8. Two approaches have been used. In the first, micromachining methods were employed to fabricate an integrated 270-810GHz frequency tripler. This includes a varactor diode contacted via an electroplated whisker, which is integrated with a stripline filter and waveguide probe. In the second approach, a specially designed Schottky diode chip incorporating the stripline filter/bias circuit is mounted in a micromachined, waveguide circuit block to form a 135-270GHz frequency doubler.