| 摘要 |
PURPOSE:To reduce a memory cell area by constituting two bits in one memory cell and by directly connecting the first and the second channel formation regions in series without interposing a semiconductor region and the like. CONSTITUTION:The memory cells M1-M4 of a mask ROM memory are provided at the intersections of a data line DL, a source line SL and each independently selected word lines W1, W2 respectively. The memory cells M1-M4 connect in series two n-channel MISFET Q which have each a separately connected gate electrode. In other words, the memory cells M1-M4 connect in series two channel formation regions which are each controlled by a separate gate electrode. Each channel formation region is set with one threshold voltage (Vth) of three threshold voltages and the information of the memory cell is written. That is, a two bit information is written since each memory cell M has two channel formation regions.
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