Terahertz phonon polaritons can be generated in ferroelectric crystal LiNbO₃ using femtosecond laser pulses. When the crystal thickness becomes comparable with or less than the terahertz wavelength, LiNbO₃ functions as an integrated chip that integrates the processes of generation, propagation, control, and detection of terahertz wave and its interaction with materials or microstructures. This provides a platform for the research and applications of terahertz waves. Moreover, by using the spatio-temporal super-resolution imaging technology, the transmission in the chip and interaction of terahertz waves with microstructures can be visualized and quantitatively analyzed. This paper reviews some works on the LiNbO₃ chip, such as the research on terahertz propagation characteristics, generation of frequency-tunable terahertz sources, and terahertz modulation using microstructures. These results demonstrate that the subwavelength LiNbO₃ chip is a promising terahertz integrated device.