Non-volatile memory device capable of storing multi-state data
First Claim
1. A non-volatile memory device capable of storing multi-state data having more than two states based on a threshold voltage, said multi-stage data corresponding to binary data, comprising:
- an input data converting means for converting N (a natural number larger than
1) binary signals into 2N multi-state data to be stored and including constant voltage generating means for generating 2N values of constant voltage corresponding to the 2N multi-state data;
an output data converting means for converting said stored multi-state data into binary signals;
a drain electrode, a source electrode and a control gate electrode;
a floating gate to and out of which electric charge is injected or subtracted, said drain, source and control gate electrodes provided around said floating gate to constitute a memory transistor for storing said multi-state data, and said drain electrode and said source electrode are formed on a semiconductor substrate;
charge injecting means for injecting electric charge into said floating gate,said charge injecting means includingfirst voltage applying means for applying zero potential to said control gate electrode and to said semiconductor substrate and for applying positive high voltage to said drain electrode in a data write operation, andsecond voltage applying means for applying zero potential to said drain electrode, to said source electrode and to said semiconductor substrate, and for applying positive high voltage to said control gate electrode in a data erase operation; and
control means for controlling the amount of electric charge to be injected by said charge injecting means, said control means including means for applying one of said 2N values of constant voltage generated by said constant voltage generating means to said source electrode to control charge injected into said floating gate during a write operation, whereinsaid threshold voltage of said memory transistor is determined based on the injected amount of electric charge.
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Abstract
The input data comprising binary data to be stored are converted into multi-state data. A voltage of a level based on the converted multi-state data is applied to a source region to perform write operation to a memory transistor. As a result, the threshold voltage of the transistor is set to a value corresponding to the potential of the source region. In read operation a drain current generated in the memory transistor is detected and the multi-state data corresponding to the current are obtained. These multi-state data are converted into binary data to be outputted as output data.
173 Citations
13 Claims
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1. A non-volatile memory device capable of storing multi-state data having more than two states based on a threshold voltage, said multi-stage data corresponding to binary data, comprising:
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an input data converting means for converting N (a natural number larger than
1) binary signals into 2N multi-state data to be stored and including constant voltage generating means for generating 2N values of constant voltage corresponding to the 2N multi-state data;an output data converting means for converting said stored multi-state data into binary signals; a drain electrode, a source electrode and a control gate electrode; a floating gate to and out of which electric charge is injected or subtracted, said drain, source and control gate electrodes provided around said floating gate to constitute a memory transistor for storing said multi-state data, and said drain electrode and said source electrode are formed on a semiconductor substrate; charge injecting means for injecting electric charge into said floating gate, said charge injecting means including first voltage applying means for applying zero potential to said control gate electrode and to said semiconductor substrate and for applying positive high voltage to said drain electrode in a data write operation, and second voltage applying means for applying zero potential to said drain electrode, to said source electrode and to said semiconductor substrate, and for applying positive high voltage to said control gate electrode in a data erase operation; and control means for controlling the amount of electric charge to be injected by said charge injecting means, said control means including means for applying one of said 2N values of constant voltage generated by said constant voltage generating means to said source electrode to control charge injected into said floating gate during a write operation, wherein said threshold voltage of said memory transistor is determined based on the injected amount of electric charge. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A non-volatile memory device capable of storing multi-state data having more than two states based on a threshold voltage comprising:
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input data converting means for converting N (a natural number larger than
1) binary signals into 2N multi-state data to be stored and including constant voltage generation means for generating 2N values of constant voltage corresponding to the 2N multi-state data;a drain electrode, a source electrode, and a control gate electrode; a floating gate to and out of which electric charge is injected or subtracted, said drain, source and control gate electrodes provided around said floating gate electrode to constitute a memory transistor, and said drain electrode and said source electrode are formed on a semiconductor substrate; charge injecting means for injecting electric charge into said floating gate, said charge injecting means including first voltage applying means for applying zero potential to said control gate electrode and to said semiconductor substrate and for applying positive high voltage to said drain electrode in a data write operation, and second voltage applying means for applying zero potential to said drain electrode, to said source electrode and to said semiconductor substrate, and for applying positive high voltage to said control gate electrode in a data erase operation; and control means for controlling the amount of electric charge to be injected by said charge injecting means said control means including means for applying one of said 2N values of constant voltage generated by said input data converting means to said source electrode to control charge injected into said floating gate during the data write operation wherein said threshold voltage is determined based on the injected amount of electric charge.
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8. A non-volatile memory device capable of storing multi-state data comprising:
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input signal converting means for converting a binary input signal into multi-state input data having more than 2 values; a memory cell for storing input data including a floating gate to and out of which electric charge is injected and subtracted, with a drain electrode, a source electrode and a control gate electrode formed around said floating gate to constitute a memory transistor; a semiconductor substrate on which said drain electrode and said source electrode are formed; writing means for writing said multi-state input data to said memory cell as said input data; reading means for reading the data written in said memory cell; and output signal converting means for converting the data read by said reading means into a binary output signal; said input signal converting means including signal converting means for converting N (a natural number larger than
1) binary signals into 2N multi-state data, andconstant voltage generating means for generating 2N values of predetermined non-zero voltage corresponding to the 2N multi-state data; and said writing means including electric charge injecting means for injecting electric charge into said floating gate, and controlling means for controlling the amount of electric charge to be injected by said electric charge injecting means including means for applying one of the 2N values of predetermined non-zero voltage to said source electrode. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification