Dual‐Scale Confinement in TiTe ₂ /C‐Sb ₃ Te Multilayers Enables Ultralow Density Variation and High Uniformity for Phase‐Change Memory

ABSTRACT Phase‐change memory (PCM) is limited by the intrinsic trade‐off among grain growth, density variation, and device uniformity. Here, a TiTe 2 /C‐Sb 3 Te multilayer nanostructure was developed to enable three‐dimensional confinement of phase transition. By synergistically integrating carbon‐induced bond stiffening with TiTe 2 interlayer confinement, nanoscale grains (∼10 nm) are effectively stabilized, leading to an ultralow density variation of 1.01%. This material‐structure co‐design strategy results in a comprehensive performance improvement, including a fast switching speed of 5 ns, low RESET energy of 6.2 pJ, and an ultralow resistance drift coefficient of 0.0019, together with stable endurance over 10 6 cycles. Notably, significantly improved resistance distribution and switching uniformity are achieved across multiple devices. The enhanced performance originates from suppressed atomic diffusion via robust C–C chains and inhibited vertical grain growth by TiTe 2 barriers. This work establishes a general strategy for coupling chemical bonding modulation with structural confinement, offering a scalable pathway toward high‐performance and reliable PCM.