Patent ID: 7102941

Claim:
A semiconductor memory device comprising: (A) a global line; (B) a memory array having (i) a local line, (ii) a decoder connected to the global line and the local line, and (iii) a memory block and a redundant block each constructed by a plurality of memory cells each having a gate electrode formed on a semiconductor layer via a gate insulating film, a channel region disposed below the gate electrode, a diffusion region disposed on both sides of the channel region and having a conductive type opposite to that of the channel region, and a memory functional unit formed on both sides of the gate electrode and having the function of retaining charges, the memory array having the function that when the decoder is usable, the global line is selectively connected to the local line in accordance with address information and, when a defective block is the memory block and the decoder is unusable, the local line is operatively disconnected from the global line and the defective block is replaced with the redundant block; and (C) a circuit for making the decoder of the defective block unusable and, only when the defective block is addressed, for making the decoder of the redundant block usable.