Parallel thin-film transistor-phase-change memory (TFT-PcRAM) is a next-generation large-capacity nonvolatile memory with a vertically integrated structure. Planar In-Ga-Zn-O (IGZO)-TFT and nanoscale PcRAM were fabricated and analyzed as active selectors and resistance-switching memory in this work. After confirming their compatibility, Ge 2 Sb 2 Te 5 (GST225) film by atomic layer deposition was combined with the IGZO-TFT to fabricate a 1 transistor-1 PcRAM parallel circuit. A direct current− voltage sweep and transfer behavior showed that the parallel IGZO-TFT/GST225-PcRAM performed depending on the gate voltage. The specific device behavior could be quantitatively understood from the parallel circuit structure. The cross-section transmission electron microscopy along the lateral and perpendicular directions indicated the localized amorphous region, confirming the phase-change mechanism. Finally, a string number simulation was performed to identify the array operation based on the single-device data. These results demonstrate the availability of parallel IGZO-TFT/GST225-PcRAM as the next-generation nonvolatile memory.