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.