SEMICONDUCTOR MEMORY DEVICE PROVIDED WITH CIRCUIT GENERATING DIFFERENT WORD LINE VOLTAGES

摘要

PROBLEM TO BE SOLVED: To store the multi-bit data and to improve reliability by automatically adjusting different word line voltages so as to keep a gate-source voltage of a memory cell to a fixed level when the threshold voltage or the different word line voltages of the memory cell are changed. SOLUTION: When data read-out is started, a signal STG becomes from a high level to a low level, and the signal NO- ACT1 is kept to the high level, and the signals NO- ACT2 and NO- ACT3 are kept to the low level succeedingly. A PMOS transistor 57 of a first word line voltage generator 100a is activated by the activated signal NO- ACT1, and thus, a node 5C is discharged through NMOS transistors 56 and 57. A detection circuit 110a detects whether or not a current flows through a dummy cell M100 to supply the current to the node ND1. The gate source voltage Vgs of the memory cell is fixed to the voltage bVoffset during respective sensing operations.