A Dual-Channel Ferroelectric-Gate Field-Effect Transistor Enabling nand -Type Memory Characteristics

We demonstrate here an oxide memory (OxiM) transistor as a new type of ferroelectric-gate field-effect transistor (FeFET), provided with a dual (top and bottom) channel, which can memorize channel conductance with a dynamic range exceeding 10⁴. This new transistor consists entirely of the following oxide-based thin films: SrRuO₃ (bottom gate electrode); Pb(Zr, Ti)O₃ (ferroelectric); ZnO (semiconductor); and SiON (gate insulator). A notable feature of the OxiM transistor is that two types of FET, i.e., a top gate-type thin-film transistor (top-TFT) and a bottom gate-type FeFET (bottom-FeFET), are stacked with a conduction layer of thin ZnO film in common. The channel conductance of the top-TFT and the bottom-FeFET can be controlled independently by the top gate and the bottom gate, respectively. We were successful in fabricating a nand memory circuit using serially connected OxiM transistors. The dual-gate structure allows disturb-free reading. Multivalued data can also be memorized in an OxiM transistor with a retention time of over 3.5 months.