A novel two-terminal high-speed nonvolatile memory device is demonstrated featuring the construction of a quasi-metal-insulator-semiconductor (q-MIS) architecture. The quasi-MIS memory takes advantage of an in situ formed amorphous AlOx interfacial layer sandwiched between p-type ZnS nanoribbons (p-ZnSNRs) and a Al electrode. Systematical optimization of the AlOx interfacial layer enables the resultant memory to show excellent memory characteristics, including a fast programming speed of <100 ns, a high current ON/OFF ratio of ∼108, a long retention time of 6 × 104 s, and good stability over 12 months. In addition, an interface-state-induced mechanism is proposed to elucidate in detail the memory characteristic for the quasi-MIS structure. This work suggests great potential of such quasi-MIS architecture for high-performance two-terminal memory, and more importantly, signifies the importance of interface engineering for the construction of novel functional nano-devices.