| 摘要 |
PURPOSE: A nonvolatile semiconductor memory device is provided to make an accurate reference level by making a configuration of a reference cell array, that is, the type of code ion implantation similar to that of a main memory cell, and to minimize an error while reading data from a semiconductor chip. CONSTITUTION: The nonvolatile semiconductor memory device comprises a reference cell transistor which is constituted to sense information stored in a memory cell and at least more than two reference cell transistor arrays where each reference cell transistor is comprised adjacently each other. The program state of the reference cell transistor is a type of a checkerboard. The reference cell transistor array is arranged at least more than two lines, and an ion implantation is performed into the reference cell transistor in order to sense binary information of the memory cell easily. And, the reference cell transistor has at least more than two threshold voltages.
|
