Channel-stacked NAND flash memory with layer selection by multi-level operation (LSM)

In this paper, the channel stacked array (CSTAR) NAND flash memory with layer selection by multi-level operation (LSM) of string select transistor (SST) is proposed and investigated to solve problems of conventional channel stacked array. In case of LSM architecture, the stacked layers can be distinguished by combinations of multi-level states of SST and string select line (SSL) bias. Due to the layer selection performed by the bias of SSL, the placement of bit lines and word lines is similar to the conventional planar structure, and proposed CSTAR with LSM has no island-type SSLs. As a result of the advantages of the proposed architecture, various issues of conventional channel stacked NAND flash memory array can be solved.