BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a schematic example of circuit configuration in the first embodiment of the nonvolatile semiconductor memory device according to the present invention.
FIG. 2 is a circuit diagram showing partial configuration of a cross-point memory cell array.
FIG. 3 is a schematic vertical sectional view of memory cells only consisting of variable resistive elements in the cross point memory cell array shown in FIG. 2.
FIG. 4 is a volt-ampere curve showing resistive characteristics of the structure shown in FIG. 3.
FIG. 5 is a view showing variations in resistance values when an experiment of unipolar switching operations was conducted on the variable resistive element to be used in the first embodiment, without going through load resistance.
FIG. 6 are two types of volt-ampere curves: one is the volt-ampere curve showing two resistive characteristics in the high resistance state and in the low resistance state when the resistive characteristics of the variable resistive element to be used in the first embodiment was measured without going through load resistance, and the other is the volt-ampere curve showing two resistive characteristics in the high resistance state and in the low resistance state when measurement was taken through load resistance.
FIG. 7 are two types of volt-ampere curves: one is the volt-ampere curve showing a load resistive characteristic of MOSFET that serves as a load resistive characteristic variable circuit, and the other is the volt-ampere curve showing two resistive characteristics of high resistance state and low resistance state of the variable resistive element to be used in the first embodiment when measurement was conducted with MOSFET as the load circuit.
FIG. 8 is a view showing variations in the resistance value when an experiment of unipolar switching operations was conducted on the variable resistive element to be used in the first embodiment, through load resistance.
FIG. 9 is a block diagram schematically showing a relation among the variable resistive element of the selected memory cell, the load circuit, and the voltage switching circuit being a target of writing in the first embodiment.
FIG. 10 is a circuit diagram showing an example of circuit configuration of the load resistance characteristic variable circuit to be used in the first embodiment.
FIG. 11 is a block diagram showing a schematic example of circuit configuration in the second embodiment of the nonvolatile semiconductor memory device according to the present invention.
FIG. 12 is a view showing variations in the resistance value when an experiment of bipolar switching operations was conducted on the variable resistive element to be used in the second embodiment, without going through load resistance.
FIG. 13 is a volt-ampere curve of the polarity dependent load resistance circuit to be used in the experiment of bipolar switching operations as shown in FIG. 14.
FIG. 14 is a view showing variations in the resistance value when an experiment of bipolar switching operations was conducted on the variable resistive element to be used in the second embodiment, through the polarity dependent load resistive circuit as the load circuit.
FIG. 15 is a block diagram schematically showing a relation among the variable resistive elements of the selection memory cell, the load circuit, and the voltage switching circuit being a target of writing in the second embodiment.
FIG. 16 is a circuit diagram showing an example of circuit configuration of the load resistive characteristic variable circuit to be used in the second embodiment.
FIG. 17 is a volt-ampere curve showing one example of the load resistive characteristic of the polarity dependent load resistive circuit that can be used as the load resistive characteristic variable circuit in the second embodiment.
FIG. 18 is a schematic cross sectional view and an equivalent circuit diagram showing one example of configuration of the 1D1R type memory cells in the third embodiment of the nonvolatile semiconductor memory device according to the present invention.
FIG. 19 is a circuit diagram showing a partial configuration of the cross-point memory cell array that uses the 1D1R type memory cells as shown in FIG. 18.
FIG. 20 is a block diagram showing a schematic example of circuit configuration in the fourth embodiment of the nonvolatile semiconductor memory device according to the present invention.
FIG. 21 is a schematic cross sectional view and an equivalent circuit diagram showing one example of configuration of the 1T1R type memory cell in the fourth embodiment.
FIG. 22 is a circuit diagram showing a partial configuration of the memory cell array 11 that uses the 1T1R type memory cells as shown in FIG. 21.
FIG. 23 is a volt-ampere curve showing the resistive characteristics of the variable resistive element having Pt/NiO/Pt structure.
FIG. 24 is a volt-ampere curve showing the resistive characteristics of the variable resistive element having W/CuOx/Pt structure.
FIG. 25 is a volt-ampere curve showing the resistive characteristics of the conventional variable resistive element capable of bipolar switching operations measured without going through the load resistance.
FIG. 26 is a volt-ampere curve showing the resistive characteristics of the conventional variable resistive element capable of bipolar switching operations measured through the load resistance.
FIG. 27 are two types of volt-ampere curves showing the resistive characteristics of the conventional variable resistive element capable of unipolar switching operations measured through the load resistance.
FIG. 28 are two types of volt-ampere curves showing the resistive characteristics of the variable resistive element capable of unipolar switching operations based on the present invention measured through the load resistance.
FIG. 29 is a volt-ampere curve showing the resistive characteristics of the variable resistive element capable of bipolar switching operations based on the present invention measured through the load resistance.