The scaling of RESET current ( $I_\mathrm RESET$ ) used for reamorphization in phase-change memory (PCM) devices has been a challenging task to meet the energy-efficient programming. The faithful prediction of $I_\mathrm RESET$ of scaled-down devices demands realistic physical models in order to examine low-power, miniaturized device characteristics, and the potential of a highly scalable PCM technology. Therefore, modeling the intrinsic interface effects, thermal boundary resistance (TBR) at the GeSbTe (GST)-metal and GST-oxide interfaces, and electrical interface resistance (EIR) at the GST-metal interface of the nanoscale PCM device is necessary. In this paper, the impact of presence and absence of TBR and EIR on $I_\mathrm RESET$ in a mushroom-type PCM device is investigated, and their usefulness on scaling is predicted for diminished devices. Reductions in $I_\mathrm RESET$ , 32% in the case of 100 nm contact diameter (CD), 45% for the 40-nm CD and 73% for the 10-nm CD are achieved by taking into account of interface effects, and these results are validated with experimental results published elsewhere. The fitted model suggests $I_\mathrm RESET$ scales down linearly with CD and necessitates for the combined effects of TBR and EIR to successfully follow the isotropic scaling in mushroom-type devices. Hence, our simulation results demonstrate the significance of TBR and EIR for a better optimization and a reliable prediction of $I_\mathrm RESET$ for low-power programming of PCM devices toward enabling next generation high-speed, high-density nonvolatile memory applications. © 1982-2012 IEEE.