Nand-cell type electrically erasable and programmable read- only memory with redundancy circuit.

摘要

A NAND-cell type electrically erasable and programmable read only memory (20) includes an array (21) of rows and columns of memory cells associated with parallel bit lines on a semiconductive substrate. Each memory cell essentially consists of a floating-gate field effect transistor having a floating gate and an insulated control gate. The memory cell array (21) is divided into a plurality of cell blocks, each of which includes NAND cell sections each including a predetermined number of a series-connected memory cell transistors. A redundancy cell section is provided which includes an array of redundancy memory cells containing at least one spare cell block. A row redundancy circuit (29) is connected to a row decoder (22), and is responsive to an address buffer (28). The redundancy circuit (30) replaces a defective block containing a defective memory cell or cells with the spare cell block.