The research project outlined in this article is developing a compact, efficient, ultra-high-speed device system using terahertz waves based on an electronic device RTD and a photonic microstructure photonic crystal (PC) Ð as an active component (source, detector, modulator) and a passive component (waveguide, coupler, filter, cavity, antenna), respectively Ð in the integrated circuits. RTD is a key device for the application of terahertz waves that can oscillate at the highest frequency among various simple electronic devices. Through their research, the team is aiming to achieve the maximum transmission rate using an RTD for wireless communication applications. As there are transmission rate limitations associated with using a simple RTD, the researchers are striving to develop a novel integrated technology to develop ultra-high-speed wireless communication systems with low power consumption using terahertz waves through the fusion of RTDs and PCs, which can be used as an ultra-low-loss terahertz integrated platform.