Ferroelectric memory

The present invention relates to a semiconductor memory and concerns a nonvolatile ferroelectric memory for storing data by using characteristics of a ferroelectric capacitor. To provide a ferroelectric memory, in which data can be positively protected even in an event of fluctuations in process parameter, time can be shortened for a reliability estimation test, and it is possible to avoid device breakage resulted from the test. A source voltage VDD is detected by using a source voltage detection circuit having a stable detection level. When a detected voltage RREFA is at or lower than a set detection level VREFA, an external input terminal XEXTCE is deactivated by using an output signal of a differential amplifier circuit to protect data. Thus, it is possible to protect data with stability.