<p>The phase change material Sb₂Te₃ (ST) has attracted considerable attention owing to its remarkable phase change speed and low thermal stability for phase change memory (PCM) applications. Many efforts have been performed to tailor the phase change properties. Unfortunately, the improvement in the thermal stability is usually accompanied by the sacrifice of the phase change speed. In this study, we co-doped of Nb and C with ST to design a highly stable and phase change speed material for practical applications. Considerably enhanced crystallization and data retention temperatures were observed in the co-doped films. In addition, no phase separation or deformation of the crystal structure were observed. Raman spectra results indicated that the typical A_1g(1) and A_1g(2) modes of the Sb–Te bonds were considerably enhanced because of the Nb substitution. Co-doped film-based devices were fabricated to evaluate their overall phase change properties. Improved operating speed and low device power consumption were observed in the device performance test. This study provides effective solutions for designing phase change materials for PCM applications.</p>