Semiconductor memory and method for driving the same

A semiconductor memory comprising:

• a memory cell block of a plurality of successively connected memory cells each including a ferroelectric capacitor having a ferroelectric film, a first electrode formed on said ferroelectric film and a second electrode formed under said ferroelectric film and a cell selecting transistor serially connected to said ferroelectric capacitor;
• data writing means for causing a first state in which said ferroelectric film of a selected ferroelectric capacitor selected by said cell selecting transistor from said plurality of ferroelectric capacitors has polarization in a direction from said first electrode to said second electrode or in a direction from said second electrode to said first electrode and has a saturated polarization value or causing a second state in which said ferroelectric film of said selected ferroelectric capacitor has polarization in the same direction as in said first state and has a zero polarization value by applying a writing voltage between a control line connected to a first common node out of two common nodes included in said memory cell block and a second common node out of said two common nodes, whereby writing a data corresponding to said first state or said second state in said selected ferroelectric capacitor;
• and
• data reading means, including a load capacitor connected to said first common node and means for applying a reading voltage between said second common node and said load capacitor, for detecting whether a selected ferroelectric capacitor selected by said cell selecting transistor from said plurality of ferroelectric capacitors is in said first state or in said second state by detecting a voltage induced in said load capacitor resulting from dividing said reading voltage in accordance with a ratio between capacitance of said selected ferroelectric capacitor and capacitance of said load capacitor, whereby reading a data stored in said selected ferroelectric capacitor.

A method for driving a semiconductor memory comprising the steps of:

• writing a data in a ferroelectric capacitor formed on a semiconductor substrate and including a ferroelectric film, a first electrode formed on said ferroelectric film and a second electrode formed under said ferroelectric film;
• and
• reading a data stored in said ferroelectric capacitor,
• wherein the step of writing a data includes a sub-step of causing a first state in which said ferroelectric film has polarization in a direction from said first electrode to said second electrode or in a direction from said second electrode to said first electrode and has a saturated polarization value or causing a second state in which said ferroelectric film has polarization in the same direction as in said first state and has a zero polarization value, whereby writing a data corresponding to said first state or said second state in said ferroelectric capacitor, and
• the step of reading a data includes a sub-step of detecting whether said ferroelectric capacitor is in said first state or in said second state, whereby reading a data stored in said ferroelectric capacitor.

A method for driving a semiconductor memory comprising the steps of:

• writing, in a memory cell block of a plurality of successively connected memory cells each including a ferroelectric capacitor having a ferroelectric film, a first electrode formed on said ferroelectric film and a second electrode formed under said ferroelectric film and a cell selecting transistor serially connected to said ferroelectric capacitor, a data in a selected ferroelectric capacitor selected by said cell selecting transistor from said plurality of ferroelectric capacitors;
• and
• reading a data stored in a selected ferroelectric capacitor selected by said cell selecting transistor from said plurality of ferroelectric capacitors,
• wherein the step of writing a data includes a sub-step of applying a writing voltage between a control line connected to a first common node out of two common nodes included in said memory cell block and a second common node out of said two common nodes, and causing a first state in which said ferroelectric film of said selected ferroelectric capacitor has polarization in a direction from said first electrode to said second electrode or in a direction from said second electrode to said first electrode and has a saturated polarization value or causing a second state in which said ferroelectric film of said selected ferroelectric capacitor has polarization in the same direction as in said first state and has a zero polarization value, whereby writing a data corresponding to said first state or said second state in said selected ferroelectric capacitor, and
• the step of reading a data includes a sub-step of applying a reading voltage between said second common node and a load capacitor connected to said first common node, and
• detecting whether said selected ferroelectric capacitor is in said first state or in said second state by detecting a voltage induced in said load capacitor resulting from dividing said reading voltage in accordance with a ratio between capacitance of said selected ferroelectric capacitor and capacitance of said load capacitor, whereby reading a data stored in said selected ferroelectric capacitor.

A semiconductor memory comprising:

• a ferroelectric capacitor formed on a semiconductor substrate and including a ferroelectric film, a first electrode formed on said ferroelectric film and a second electrode formed under said ferroelectric film;
• data writing means for causing a first state in which said ferroelectric film has polarization in a direction from said first electrode to said second electrode or in a direction from said second electrode to said first electrode and has a saturated polarization value or causing a second state in which said ferroelectric film has polarization in the same direction as in said first state and has a different polarization value corresponding to said first state, whereby writing a data corresponding to said first state or said second state in said ferroelectric capacitor;
• and
• data reading means for reading a data stored in said ferroelectric capacitor by detecting whether said ferroelectric capacitor is in said first state or in said second state.