| 摘要 |
<p>PURPOSE:To store the information amount of one bit or more in a single memory cell transistor TR by selecting one of four types of threshold value of the memory cell TRs based on the data to be written. CONSTITUTION:The memory cell TR 17-19 constructing a mask ROM 10 have four types of threshold value voltage VT1-VT4. When the TR 17 is selected, for example, four types of electric potential VG1<VG2<VG3<VG4 which satisfy the relation VT1<VG1<VT2<VG2<VT3<VG3<VT4-<VG4 are supplied to a gate 13. Then the electric potential of the gate 13 is detected when the gate line aluminum 11 is set at L, and a single memory cell TR can store the information amount of one bit or more.</p> |
