| 摘要 |
PROBLEM TO BE SOLVED: To suppress the increase of a memory cell area to min. and reduce the production cycle time by applying read voltages to word lines with holding selected bit lines at specified precharge potential. SOLUTION: A mask ROM comprises parallel word lines WL0-WL3 and bit lines BO0-BL3 crossing the word lines and memory cells M00 -M03 , M30 -M33 disposed like a matrix on the intersections of the word lines and bit lines. In the cells stored data are set according to the existence of via-contacts. A polysilicon layer or first and second metal wiring layers thereon are previously formed, write data for the cells are acquired and remaining process is followed to code the data, and mask ROM is then formed. This greatly reduces the production cycle time, hence improves the integration degree and forms a mask ROM with approximately the same area as by the diffusion system, thereby reducing the memory chip area and cost. |
