Nonvolatile semiconductor memory device and programming method

摘要

A nonvolatile semiconductor memory device of the charge trap type is initialized by reading the memory cells in the device to determine which charge traps hold less than a predetermined minimum charge and injecting charge into these charge traps until all of the charge traps in the device hold at least the predetermined minimum charge. The charge traps are then programmed selectively with data. The initialization procedure shortens the programming procedure by narrowing the initial distribution of charge in the charge traps, and leads to more reliable reading of the programmed data.

主权项

1. A nonvolatile semiconductor memory device comprising:
a plurality of bit lines; a plurality of memory cells connected to the bit lines, the memory cells including respective charge traps for storing charge representing data values; and a controller for programming the memory cells by injecting charge into their charge traps via the bit lines, and reading the memory cells by detecting the charge stored in their charge traps; wherein before programming data into the memory cells, the controller places the memory cells in an initial state by reading the memory cells to determine which charge traps hold less than a predetermined minimum charge and injecting charge into the charge traps holding less than the predetermined minimum charge until all of the charge traps hold at least the predetermined minimum charge.