Nitride superconductors such as NbN, NbTiN, and TiN have attracted attention as low-loss superconductors in superconducting quantum circuits. We have developed a technique for epitaxially growing TiN films on Si(100) substrates [1], which is being used in a superconducting quantum processor under development in the Q-LEAP Flagship Project, a national project for the realization of quantum computers in Japan [2]. We also developed NbN/AlN/NbN epitaxial junctions on Si(100) substrate with a TiN buffer layer, where the AlN tunnel barrier has a cubic structure. Such crystallized AlN tunnel barriers have the potential to improve the coherence time of superconducting qubits compared to amorphous oxide tunnel barriers. The superconducting transition temperature TC of NbN is also as high as 16 K, which is more than an order of magnitude higher than that of Al at 1 K. So superconducting qubits with NbN/AlN/NbN epitaxial junctions have the potential to operate at 1 K, which is never achievable with Al/AlOX/Al junctions. We have fabricated C-shunt flux qubits based on epitaxially grown NbN/AlN/NbN junctions on Si (100) substrates using TiN buffer layers and successfully observed an energy relaxation time T1 of 16.3 us and a spin-echo dephasing time T2E of 21.5 us [3]. In this talk, we introduce recent progress in superconducting qubits based on nitride superconductors as a new material platform for future quantum technologies.