Nonvolatile semiconductor memory circuit including a reliable sense

Abstract

A nonvolatile memory device has a memory cell having its gate connected to a word line, its source connected to a ground potential and its drain connected to a power supply voltage via a bit line and a dummy cell having its gate connected to the word line, its source connected to the source potential and its drain connected to the power supply voltage via a dummy bit line. The bit line and the dummy bit line are connected to reset and set terminals of a sense amplifier circuit comprising a flip-flop circuit and a latch type of sense amplifier. The conductance of the dummy cell is made smaller than that of the memory cell so that the speed at which the potential on the bit line is lowered depends on the state of injection of electrons into the memory cell as compared with the speed at which the potential on the dummy bit line at a time of reading data. The flip-flop circuit is reset or set in accordance with the speed at which the potential on the bit line is lowered and then the latch type of sense amplifier operates to latch the output of the flip-flop circuit and output it as read data.