Millimeter-wave compact, high quality (Q-) Substrate Integrated Waveguide (SIW) cavity is proposed in 0.18-µm CMOS technology. Compact size of the SIW cavity resonator is achieved first by taking 1/16th parts of the standard SIW and employing folded ridge structure. Two prototypes of the proposed cavity resonator with different feeding structures were fabricated and measured. The measurement results present a reflection coefficient lower than -22 dB and the external Q-factor greater than 60 in both cases. Experimentally, it is verified that due to the low losses associated with the top feed structure, it presents better return losses and Q-factor than the transition feed structure. Moreover, the active area of the fabricated cavity resonators without measuring pads are only 0.024 mm2, which is only 0.563% when compared to the standard SIW cavity.