Patent ID: 7295467

Claim:
For an electrically programmable non-volatile multi-level memory device including a plurality of non-volatile multi-level memory cells, each of the multi-level memory cells having a non-volatile memory storage portion for determining an electrically alterable voltage threshold value, electrons being capable of being injected into the non-volatile memory storage portion, a method of operating the electrically alterable non-volatile multi-level memory device, comprising: determining a status of at least one non-volatile multi-level memory cell of the plurality of non-volatile multi-level memory cells to a plurality of states including at least a first level state of an erased state, a second level state, a third level state and a fourth level state of a plurality of programmed states, a level distance to the fourth level state from the first level state being larger than that to the third level state from the first level state and a level distance to the third level state from the first level state being larger than that to the second level state from the first level state, and controlling an electrically alterable voltage threshold value of at least one non-volatile multi-level memory cell to a value which responds to a higher bit and a lower bit of digital data to be stored in the least one non-volatile multi-level memory cell, wherein the higher bit of the digital data to be stored in the at least one non-volatile multi-level memory cell is digital data of one block data and the lower bit of the digital data to be stored in the least one non-volatile multi-level memory cell is digital data of another block data, and wherein the one block data and the other one block data are sent from an exterior of the electrically alterable non-volatile multi-level memory device in different timings.