| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the dispersion of distribution of threshold voltage of a memory cell by preventing electrons from injecting into a floating gate of the other memory cell in which threshold voltage reaches the prescribed value while memory cells in which threshold voltage does not reach the prescribed value is programmed again, when a memory cell is programmed by a program means of injecting electrons. SOLUTION: When electrons are injected into a floating gate of a memory cell, a signal P is made 1ogic '11'. The prescribed time elapses and while the signal P is logic '0', an injection state of electrons for the floating gate is checked. At the time. a potential VP' is raised, and higher voltage than voltage of the previous time is given to a row line. A column line connected to a memory cell in which sufficient electrons are injected is set to a potential of V3, injecting electrons into a floating gate is prevented, electrons are injected into a floating gate in which injected electrons are insufficient. Until threshold voltage of all memory cells reaches the prescribed value, injecting electrons into a floating gate is repeated.</p> |
