Two-transistor flash cell for large endurance application

摘要

An nonvolatile memory device having improved endurance is comprised of an array of nonvolatile memory cells arranged in rows and columns. Each memory cell of each row is connected to a word line and a source select line, and each memory cell of each column connected to a first bit line and a second bit line. Each memory cell is composed of a first transistor and second transistor. The first and second transistors have control gate connected to the word line receive a word line voltage, a source connected the source select line to receive a source line voltage, and a floating gate onto which an electronic charge is placed representing a data bit stored within the nonvolatile memory device. The first transistor has a drain connected the first bit line to receive a first bit line voltage and the second transistor a drain connected to the second bit line to receive a second bit line voltage. Each memory cell has a floating gate connector joining the floating gate of the second transistor to the floating gate of the second transistor. The nonvolatile memory device has a voltage controller programs the each memory cell by programming the first transistor and reading the second transistor. Alternately the voltage controller employs a two step programming method by programming the first transistor for a short period of time and then programming the second transistor for second short period of time and then reading from the second transistor.