MASK ROM, SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE USING IT, AND METHOD OF MANUFACTURING THE MASK ROM

摘要

PROBLEM TO BE SOLVED: To provide a mask ROM which can realize memory capacity development or memory circuit characteristic tuning in response to a request from a customer by arbitrarily selecting a plurality of kinds of circuits in a ROM rewriting process and a semiconductor integrated circuit device using the mask ROM. SOLUTION: A mask ROM mounted on logic, microcomputer, etc., and adopting a memory capacity developing system is constituted of a memory array 1 composed of memory cells and a memory address control circuit block 2 which controls the address of the array 1 and the block 2 is provided with memory address control circuits 4 and 5 for 23k and 16k bits and switch MOSFETs 6 and 7 having the same structure as the memory cells of the array 1 have. The thresholds of switch MOSFETs 6 and 7 can be adjusted in response to a request from a customer by using the photomask of a ROM rewriting process depending upon whether ion implantation is performed or not.