Semiconductor memory and writing method and reading method for the same

A writing method for a semiconductor memory comprising a memory cell including a capacitor element and a transistor element, the capacitor element using a ferroelectric material such that the quantity of residual dielectric polarization in an electroless state in a hysteresis characteristic is not reduced to less than a predetermined threshold value until after the lapse of the time of a refreshing cycle including at least plural clocks, the semiconductor memory having a sense amplifier for performing refreshing when a detected value of a bit line output is equal to or larger than a threshold value, the method comprising:

• switching a word line to a high voltage and turning on the transistor element of the memory cell, thus setting a state of continuity;
• turning on a switching element on abit line, thus setting a state of continuity;
• applying a desired high voltage to the bit line and a plate line at desired timing, thus performing writing;
• switching all the bit line and the plate line to a low voltage;
• and
• switching the word line to a low voltage and turning off the transistor element of the memory cell, thus setting a state of discontinuity.

A reading method for a semiconductor memory comprising a memory cell including a capacitor element and a transistor element, the capacitor element using a ferroelectric material such that the quantity of residual dielectric polarization in an electroless state in a hysteresis characteristic is not reduced to less than a predetermined threshold value until after the lapse of the time of a refreshing cycle including at least plural clocks, the semiconductor memory having a sense amplifier for performing refreshing when a detected value of a bit line output is equal to or larger than a threshold value, the method comprising:

• turning off a switching element on a bit line, thus setting a state of discontinuity;
• switching a word line to a high voltage and turning on the transistor element of the memory cell, thus setting a state of continuity;
• detecting an output of the bit line by the sense amplifier, judging whether or not the detected value is equal to or larger than the predetermined threshold value, outputting a refreshed high voltage if the detected value is equal to or larger than the threshold value, and outputting a low voltage if the detected value is less than the threshold value, thus performing reading;
• applying a high voltage to a plate line, thus reading out data;
• switching all the bit plate and the plate line to a low voltage;
• and
• switching the word line to a low voltage and turning off the transistor element of the memory cell, thus setting a state of discontinuity.