Fully integrated single-pole-double-throw and single-pole-triple-throw InP/InGaAs PIN switches have been designed and fabricated using a newly proposed BCB-based 3D MMIC technology. The chip sizes of the fabricated InP/InGaAs PIN switches, which show good and broadband RF characteristics, have been significantly reduced compared to those of conventional GaAs-based switches. The results indicate the potential of the proposed 31) MMIC technology for compact embedded MMIC applications.