Non-volatile semiconductor memory having an array of non-volatile memory cells and method for driving the same
First Claim
1. A non-volatile semiconductor memory comprising:
- an array of non-volatile memory cells arranged in columns and rows, wherein each said non-volatile memory cell has a transistor and a capacitance section, said transistor being composed of, at least, a gate, a channel region, a source, and a drain;
a plurality of wordlines, wherein each said wordline is connected to each of said gates in a row of said memory cell array;
a plurality of bitlines, wherein each said bitline is connected to each of said drains in a column of said memory cell array;
a plurality of sourcelines, wherein each said sourceline is connected to each of said sources in a row of said memory cell array;
a row decoder circuit for selecting among said plurality of wordlines;
a column decoder circuit for selecting among said plurality of bitlines;
a source decoder circuit for selecting among said plurality of sourcelines;
a plurality of anisotropic resistance sections;
wherein;
each said anisotropic resistance section is arranged in a path from a said bitline to a said sourceline through a said transistor, said anisotropic resistance section is arranged between said channel region of the transistor and said bitline;
each said anisotropic resistance section has voltage-current properties which are different for different levels of voltages applied across said anisotropic resistance section;
each said anisotropic resistance section has a forward direction in which a current flows therethrough with lesser resistance and a reverse direction in which a current flows therethrough with greater resistance, said anisotropic resistance section has properties such that resistance to a current flowing from said memory cell to said bitline is larger than resistance to a current flowing from said bitline to said memory cell.
1 Assignment
0 Petitions
Accused Products
Abstract
An array of non-volatile memory cells arranged in rows and columns is provided. Each memory cell is composed of a transistor made up of a gate, a source, and drain and a capacitance section. Each memory cell is connected to a row decoder through a wordline, to a column decoder through a bitline, and to a source decoder through a sourceline. Arranged in a path extending from a bitline to a sourceline through a transistor is an anisotropic resistance section, e.g., a diode, exhibiting different voltage-current characteristics for different levels of voltages applied thereacross. Because of such arrangement, leakage current occurring to a deselected memory cell in a reading operation can be reduced or can be eliminated. Read errors due to leakage current can be avoided and the power consumption can be reduced.
62 Citations
12 Claims
-
1. A non-volatile semiconductor memory comprising:
-
an array of non-volatile memory cells arranged in columns and rows, wherein each said non-volatile memory cell has a transistor and a capacitance section, said transistor being composed of, at least, a gate, a channel region, a source, and a drain; a plurality of wordlines, wherein each said wordline is connected to each of said gates in a row of said memory cell array; a plurality of bitlines, wherein each said bitline is connected to each of said drains in a column of said memory cell array; a plurality of sourcelines, wherein each said sourceline is connected to each of said sources in a row of said memory cell array; a row decoder circuit for selecting among said plurality of wordlines; a column decoder circuit for selecting among said plurality of bitlines; a source decoder circuit for selecting among said plurality of sourcelines; a plurality of anisotropic resistance sections; wherein; each said anisotropic resistance section is arranged in a path from a said bitline to a said sourceline through a said transistor, said anisotropic resistance section is arranged between said channel region of the transistor and said bitline; each said anisotropic resistance section has voltage-current properties which are different for different levels of voltages applied across said anisotropic resistance section; each said anisotropic resistance section has a forward direction in which a current flows therethrough with lesser resistance and a reverse direction in which a current flows therethrough with greater resistance, said anisotropic resistance section has properties such that resistance to a current flowing from said memory cell to said bitline is larger than resistance to a current flowing from said bitline to said memory cell. - View Dependent Claims (2, 3, 4, 5, 12)
-
-
6. A non-volatile semiconductor memory according to claim wherein:
-
drains of each of pairs of memory cells in adjacent relationship of said memory cells are connected to a common bitline; said pairs of memory cells are placed in checkerboard arrangement to form an array structure; two wordlines are arranged to a single sourceline, and sources of memory cells, connected to said wordlines located next to said source line, are connected to said source line. - View Dependent Claims (7)
-
-
8. A method of driving a non-volatile semiconductor memory;
said non-volatile semiconductor memory comprising; an array of non-volatile memory cells arranged in columns and rows, wherein each said non-volatile memory cell has a transistor and a capacitance section, said transistor being composed of, at least, a gate, a source, and a drain; a plurality of wordlines, wherein each said wordline is connected to each of said gates in a row of said memory cell array; a plurality of bitlines, wherein each said bitline is connected to each of said drains in a column of said memory cell array; a plurality of sourcelines, wherein each said sourceline is connected to each of said sources in a row of said memory cell array; a row decoder circuit for selecting among said plurality of wordlines; a column decoder circuit for selecting among said plurality of bitlines; a source decoder circuit for selecting among said plurality of sourcelines; a plurality of anisotropic resistance sections; wherein; each said anisotropic resistance section is arranged in a path from a said bitline to a said sourceline through a said transistor; each said anisotropic resistance section has voltage-current properties which are different for different levels of voltages applied across said anisotropic resistance section; each said anisotropic resistance section has a forward direction in which a current flows therethrough with lesser resistance and a reverse direction in which a current flows therethrough with greater resistance; said drive method comprising the steps of; selecting, from among said plurality of bitlines, a bitline associated with a memory cell to be read by means of said column decoder circuit; selecting, from among said plurality of sourcelines, a sourceline associated with said memory cell by means of said source decoder circuit; setting the electric potential of said selected bitline and the electric potential of said selected sourceline such that the electric potential relationship of said selected bitline versus said selected sourceline agrees with said forwarding direction of said anisotropic resistance section, and setting the higher of said selected bitline'"'"'s electric potential and said selected sourceline'"'"'s electric potential as a reading electric potential; setting the electric potential of deselected sourcelines to an electric potential level above the lower of said selected bitline'"'"'s electric potential and said selected sourceline'"'"'s electric potential but below said reading electric potential. - View Dependent Claims (9, 10)
-
11. A method of driving a non-volatile semiconductor memory;
said non-volatile semiconductor memory comprising; an array of non-volatile memory cells arranged in columns and rows, wherein each said non-volatile memory cell has a transistor and a capacitance section, said transistor being composed of, at least, a gate, a source, and a drain; a plurality of wordlines, wherein each said wordline is connected to each of said gates in a row of said memory cell array; a plurality of bitlines, wherein each said bitline is connected to each of said drains in a column of said memory cell array; a plurality of sourcelines, wherein each said sourceline is connected to each of said sources in a row of said memory cell array; a row decoder circuit for selecting among said plurality of wordlines; a column decoder circuit for selecting among said plurality of bitlines; a source decoder circuit for selecting among said plurality of sourcelines; a plurality of anisotropic resistance sections; wherein; each said anisotropic resistance section is arranged in a path from a said bitline to a said sourceline through a said transistor; each said anisotropic resistance section has voltage-current properties which are different for different levels of voltages applied across said anisotropic resistance section; each said anisotropic resistance section has a forward direction in which a current flows therethrough with lesser resistance and a reverse direction in which a current flows therethrough with greater resistance wherein; said forward direction of said anisotropic resistance section is formed such that voltage on the bitline side is greater than voltage on the sourceline side; said drive method comprising the steps of; bringing an erased memory cell to having a negative threshold voltage; selecting, from among said plurality of bitlines, a bitline associated with a memory cell to be read by means of said column decoder circuit; selecting, from among said plurality of sourcelines, a sourceline associated with said memory cell by means of said source decoder circuit; bringing the electric potential of all of said wordlines to a ground level; increasing the electric potential of said selected bitline; bringing the electric potential of said selected sourceline to said ground level; bringing the electric potential of deselected bitlines to said ground level; passing an electric current between said selected bit line and said selected sourceline thereby to generate hot electrons for increasing said memory cell'"'"'s threshold voltage.
Specification