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Abstract

For the purpose of converting ferroelectric memory between (use as) RAM and ROM, a method of manufacturing a read-only memory (ROM) using a ferroelectric memory is realized by a chip assembly process to perform chip assembly for ferroelectric memory; a data writing process to write data to the ferroelectric memory after the chip assembly process; and a first heat treatment process to subject the ferroelectric film of ferroelectric memory, after the data writing process, to a heat treatment at a heat treatment temperature T1 (.degree. C.) lower than the phase transition temperature T.sub.c (.degree. C.) of the ferroelectric film. Further, a second heat treatment process is conducted in a method of manufacturing RAM using ferroelectric memory which has been converted into ROM, for subjecting the ferroelectric film of ferroelectric memory, which has been converted into ROM through the above processes, to a second heat treatment process, entailing heating of the ferroelectric film at a heat treatment temperature T2 (.degree. C.) equal to or higher than the phase transition temperature T.sub.c (.degree. C.) of the ferroelectric film.

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First Claim