An innovative, ultra-low phase-noise, fully integrated single-chip cavity oscillator is proposed. The cavity is built on a standard MMIC process and has a quality factor of 120 at 50 GHz, and an insertion loss of 7 dB. This proposed technique is very well suited for MMW applications with emphasis on the frequency range 50-100 GHz. The achievable phase noise at 50 GHz is -112 dBc/Hz at 100 KHz offset. This is at least 10dB better than the best fully integrated oscillator reported today. To our knowledge this is the first ever implementation of a waveguide cavity on standard MMIC process. This new technique will allow the realization of ultra-small, high-performance integrated oscillators for future market demands. The oscillator can be readily integrated with digital blocks to form a Phase Locked Oscillator (PLO). The PLO will consist of a cavity oscillator, phase frequency detector, prescaler, and a loop filter. All components can be integrated on InP HBT process.