A data storage device is disclosed that comprises a cross-point memory array formed on a dielectric substrate material. The cross-point memory array comprises first and second sets of transverse electrodes separated by a storage layer including at least one semiconductor layer. The storage layer forms a non-volatile memory element at each crossing point of electrodes from the first and second sets. Each memory element can be switched between low and high impedance states, representing respective binary data states, by application of a write signal in the form of a predetermined current density through the memory element. Each memory element includes a diode junction formed in the storage layer, at least whilst in the low impedance state. A plurality of the data storage devices can be stacked and laminated into a memory module providing inexpensive high capacity data storage. Such a memory module can be employed in an archival data storage system in which the memory module provides a write-once data storage unit receivable in an appliance or interface card.