A regular capacitor is saturated by an electric charge of a regular memory cell holding a high logic level and is not saturated by an electric charge from the regular memory cell holding a low logic level. A reference capacitor is saturated by the electric charge from a reference memory cell holding the high logic level. A differential sense amplifier differentially amplifies a difference between a regular read voltage read from the regular capacitor and a voltage which is lower by a first voltage than a reference read voltage being a saturation voltage read from the reference capacitor, and generates logic of data held in the memory cell. Accordingly, a difference between the reference voltage and the read voltage corresponding to the low logic level can be made relatively large. As a result, it is possible to improve a read margin.