In this paper, we report design, development and fabrication of high-performance Ka-band micromachined patch antennas using monolithic microwave integrated circuit (MMIC)-compatible process technology. The main emphasis of this paper is to use radio frequency (RF) sputtering as the potential metal-dielectric film deposition process for rapid prototyping of many antenna structures in the absence of access to a well-established MEMS foundry. The fabricated antennas exhibited 4%-5% of impedance bandwidth, which is much wider than the one fabricated on bulk high-index substrates.