32-MBIT VERY HIGH-DENSITY MASK ROM

This paper describes a 32 Mbit very high density mask programmable ROM, mu-PD23C32000CZ/DZ. To realize a 32 Mbit of very high density, the authors developed a new isolation method, "Super Isolation." Using this method a very small cell size of 2.38-mu-m2 has been realized. As a result, the parasitic capacitance of word line has been reduced to 70% of the previous memory cell. The authors also developed a new sense amplifier suitable for small cell current mask ROM, and have thus realized a 32 Mbit mask ROM with an access time of 200 ns and high reliability.