| 摘要 |
In an FLOTOX type non-volatile memory circuit, while a data writing voltage is low, even when a difference between a threshold voltage of a non-volatile memory element under enhancement state and a threshold voltage thereof under depletion state is small, the data can be surely read out from the non-volatile memory element in a high speed. Also, a total data rewritable time can be increased. In the non-volatile memory circuit, since 1-bit data is held by using two sets of non-volatile memory elements capable of storing thereinto data having a complementary relationship with each other, even when a difference between threshold voltages of these two non-volatile memory elements is small, the data can be surely read thereof. When data is read by using a differential type sense amplifier, potentials at a Data line and a DataX line are entered to two inputs of this sense amplifier, so that even such a small potential difference can be detected. As a result, such data can be read which is stored in a pair of non-volatile memory elements whose data writing depths are shallow, namely, a small threshold voltage difference between a depletion state and an enhancement state. Also, even when the data writing depth is shallow, since the data can be read from the non-volatile memory element pair, the data writing voltage can be lowered, and the stress given to a tunnel oxide film can be reduced, so that a total data rewritable time can be increased.
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