We demonstrate a sub-terahertz (THz) and THz integration platform based on micromachined waveguides on silicon. The demonstrated components in the frequency range 225–325 GHz include waveguides, filters, waveguide vias, and low-loss transitions between the waveguide and the monolithic integrated circuits. The developed process relies on microelectromechanical systems manufacturing methods and silicon wafer substrates, promising a scalable and cost-efficient system integration method for future sub-THz and THz communication and sensing applications. Low-temperature Au/In thermo-compression and Au–Au laser bonding processes are parts of the integration platform enabling integration of millimeter-wave monolithic integrated circuits.