Highly Scalable 3-D NAND-NOR Hybrid-Type Dual Bit per Cell FlashMemory Devices with an Additional Cut-Off Gate

摘要

In this work, a nonvolatile memory (NVM) device of novel structure in 3 dimensions is introduced,and its operation physics is validated. It is based on a pillar structure in which two identical storagenodes are located for dual-bit operation. The two storage nodes on neighboring pillars are controlledby using one common control gate so that the space between silicon pillars can be further reduced.For compatibility with conventional memory operations, an additional cut-off gate is constructedunder the common control gate. This is considered as the ultimate form for a 3-D nonvolatilememory device based on a double-gate structure. The underlying physics is explained, and theoperational schemes are validated in various aspects by using a numerical device simulation. Also,critical issues in device design for higher reliability are discussed.