Phase-change random access memory is a promising technique to realize universal memory and neuromorphic computing, where the demand for robust multibit programming drives exploration for high-accuracy resistance control in memory cells. Here in Sc x Sb 2 Te 3 phase-change material films, we demonstrate thickness-independent conductance evolution, presenting an unprecedently low resistance−drift coefficient in the range of ∼10 −4 −10 −3 , ∼3−2 orders of magnitude lower compared to conventional Ge 2 Sb 2 Te 5 . By atom probe tomography and ab initio simulations, we unveiled that nanoscale chemical inhomogeneity and constrained Peierls distortion together suppress structural relaxation, rendering an almost invariant electronic band structure and thereby the ultralow resistance drift of Sc x Sb 2 Te 3 films upon aging. Associated with subnanosecond crystallization speed, Sc x Sb 2 Te 3 serves as the most appropriate candidate for developing high-accuracy cache-type computing chips. KEYWORDS: Sc x Sb 2 Te 3 phase-change materials, atom probe tomography, chemical heterogeneity, resistance drift

Phase‐change random‐access memory (PCRAM) devices suffer from pronounced resistance drift originating from considerable structural relaxation of phase‐change materials (PCMs), which hinders current developments of high‐capacity memory and high‐parallelism computing that both need reliable multibit programming. This work realizes that compositional simplification and geometrical miniaturization of traditional GeSbTe‐like PCMs are feasible routes to suppress relaxation. While to date, the aging mechanisms of the simplest PCM, Sb, at nanoscale, have not yet been unveiled. Here, this work demonstrates that in an optimal thickness of only 4 nm, the thin Sb film can enable a precise multilevel programming with ultralow resistance drift coefficients, in a regime of ≈10−4–10−3. This advancement is mainly owed to the slightly changed Peierls distortion in Sb and the less‐distorted octahedral‐like atomic configurations across the Sb/SiO2 interfaces. This work highlights a new indispensable approach, interfacial regulation of nanoscale PCMs, for pursuing ultimately reliable resistance control in aggressively‐miniaturized PCRAM devices, to boost the storage and computing efficiencies substantially.