he evolution of wireless communication toward 6G requires operation at millimeter-wave and sub-terahertz frequencies to enable multi-gigahertz bandwidths and terabit-per-second data rates. Glass-interposer-based packaging has emerged as an attractive platform for these applications due to its low electrical loss, fine feature capability, and scalable manufacturing. This dissertation investigates the modeling, fabrication, and characterization of ultra-thin millimeter-wave passive components and antenna systems implemented on laminated glass substrates, with a focus on D-band operation. Broadband electrical characterization of low-loss dielectric materials is performed over 50–220 GHz and temperatures from −25 °C to 75 °C, providing accurate material properties for sub-terahertz design. Design considerations and performance trade-offs of planar and guided interconnects, including microstrip lines, coplanar waveguides, and substrate-integrated waveguides, are examined up to 220 GHz. A novel vertical via-less interconnect architecture is introduced to enable contactless signal transmission across glass cores and is experimentally validated up to 170 GHz. The dissertation also presents ultra-thin end-fire antenna arrays operating from 110–170 GHz, including passive arrays and beamforming arrays employing metasurface radiators. A laser-based process for forming through-glass vias is developed to realize substrate-integrated waveguide feeding networks. Probe-station-based techniques are extended to enable measurement of boresight gain and normalized three-dimensional radiation patterns of end-fire antennas at sub-terahertz frequencies. The measured results show strong agreement with simulations and are contrasted with state-of-the-art implementations. With the capability of embedding dies within the glass cores, this work establishes glass interposers as a viable platform for next generation sub-terahertz packaging.