A semiconductor memory comprises a plurality of sub banks each including one or more rows of memory bit cells connected to a set of local bit lines, wherein the sub banks share a same set of global bit lines for reading/writing data from/to the memory bit cells of the sub banks. The semiconductor memory chip further comprises a plurality of switch elements for each of the sub banks, wherein each of the switch elements connects the local bit line and the global bit line of a corresponding one of the memory bit cells in the sub bank for data transmission between the local bit line and the global bit line. The semiconductor memory chip further comprises a plurality of bank selection signal lines each connected to the switch elements in a corresponding one of the sub banks, wherein the bank selection signal lines carry a plurality of bank selection signals to select one of the sub banks for data transmission between the local bit lines and the global bit lines. The invention further comprises a high density memory structure.