Flash memory and program verify method for flash memory

Abstract

In conventional memory arrays in which a bit line is shared by memory cells, a cell current flows over into neighbor cell(s) in a program verify process, and therefore, the threshold of a memory cell to be programmed is erroneously determined to be lower. Therefore, in a program verify process, a control circuitwrites a fail value to a neighbor cell bufferwhen all neighbor cell(s) having an offset of n or less from a memory cell to be programmed are in the erased state, and when otherwise, writes a pass value to the neighbor cell buffer. The control circuitverifies input write data and also verifies data stored in the neighbor cell buffer(s). In the latter verify process, a verify voltage higher than an ordinary one is used to compensate for the leakage of cell current.