Olympus Optical Company, Ltd.

Yoshihiro Ishibashi

Hideo Adachi

Masayoshi Omura

A ferroelectric memory device according to the present invention includes memory cells. Each memory cell is constructed such that a lower electrode is formed on a silicon substrate, a ferroelectric capacitor having a hysteresis characteristic with at least two non-linear characteristic portions is formed on the lower electrode, and an upper electrode is formed on the ferroelectric capacitor. The memory cells are arranged in a matrix and are provided with a column switching controller and a row switching controller. These controllers are connected via a switching circuit to a write circuit, a read circuit and a detector. When a voltage lower than a coercive voltage is applied to the memory cells, the data storage states of the memory cells are discriminated on the basis of the difference in differential dielectric constants between '1' and '0', thus reading out the data in a non-destructive manner. In the ferroelectric memory device with this structure, an asymmetrical amplitude waveform voltage of a positive voltage lower than a coercive voltage and a negative voltage of an amplitude smaller than the amplitude of the positive voltage is applied to the ferroelectric film on which data is recorded, thereby reading out the data in a non-destructive manner.

Ferroelectric memory device

An acoustic device has an acoustic wave propagating medium exhibiting elastic abnormality in the vicinity of a Curie temperature. It is desirable that such an acoustic wave propagating medium be formed of a ferroelectric substance or a high-elastic substance and, in particular, have a Curie temperature at normal temperatures. For example, such ferroelectric substance is a solid solution expressed by Cs(Pb.sub.1-x Sr.sub.x)(Cl.sub.1-y Br.sub.y).sub.3 or (Bi.sub.1-x Dy.sub.x)VO.sub.4. By changing values of x and y appropriately, the Curie temperature of the solid solution can be varied, and an acoustic wave propagating medium meeting the purpose of use can be obtained. In such an acoustic wave propagating medium, an elastic coefficient C.sup.P at the time of constant polarization differs greatly from an elastic coefficient C.sup.E at the time of a constant electric field in the vicinity of the Curie temperature. Accordingly, the propagation velocity of acoustic waves is greatly different, too. By varying the elastic coefficients of the acoustic wave propagating medium, various novel acoustic devices utilizing the above characteristics can be obtained.

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Nagoya, Japan

Yoshihiro Ishibashi