| 摘要 |
A semiconductor read-only memory (ROM) device for permanent storage of multi-level coded data and a method of fabricating the same are provided. The ROM device is specifically devised for permanent storage of multi-level coded data that are represented by more than two logic states. The ROM device includes a semiconductor substrate formed an array of spaced major gate structures above the channel regions, and a plurality of minor gate structures formed between the major gate structures above the channel regions. Each of the major gate structures and one neighboring minor gate structure are in combination associated with one memory cell of the ROM device. The word lines are connected to the memory cells in such a manner that for those memory cells that are set to a first logic state, the word lines are connected to the associated major structures only; for those that are set to a second logic state, the word lines are connected to the associated minor structures only; for those that are set to a third logic state, the word lines are connected to both of the associated major and minor structures; and for those that are set to a fourth logic state, the word lines are isolated from the associated major and minor structures. The method requires only one pass of the mask-programming process to complete the coding of the data into the ROM device. Ref: 1325-US-PA/FINAL
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