This paper presents a terahertz (THz) transmitter (Tx) and receiver (Rx) chipset operating around 400 GHz in 0.13- μm SiGe BiCMOS technology. The Tx chip consists of a voltage-controlled oscillator, a buffer, a modulator, a power amplifier, a frequency tripler, and a substrate integrated waveguide (SIW) antenna. This antenna has an additional high-pass filtering characteristic to suppress the unwanted fundamental (f0) and second harmonic (2f0) signals by 50 and 30 dB, respectively. The Rx chip includes a proposed reconfigurable SIW antenna and a novel two-mode subharmonic mixer with ~ 5-dB reduction of conversion loss. The Rx chip consumes 50 nA from a 1.2-V supply. The measurement results of the Tx and Rx chips and a back-to-back test of the Tx/Rx chipset show the feasibility and pave the way of implementing a fully integrated THz system in silicon technology for mass production.