Phase change memory device
A phase change memory device, comprising a phase change memory device; a semiconductor substrate; a MOS transistor disposed at each intersection of a plurality of word lines and a plurality of bit lines arranged in a matrix form; a plurality of phase change memory elements for storing data of a plurality of bits, each formed on an upper area opposite to a diffusion layer of the MOS transistor in a phase change layer made of phase change material; a lower electrode structure for electrically connecting each of the plurality of phase change memory elements to the diffusion layer of the MOS transistor.
1. A phase change memory device, comprising:
a semiconductor substrate;
a MOS transistor disposed at an intersection of a word line and a bit line;
multiple phase change memory elements electrically connected to one diffusion layer of said MOS transistor, for each of which read and write operations can be individually controlled; and
a lower electrode structure electrically connecting each of said multiple phase change memory elements to said one diffusion layer, including one common plate disposed opposite to said plurality of phase change memory elements, one or more first plugs connecting said diffusion layer of said MOS transistor to said common plate, and a plurality of second plugs connecting said common plate to said plurality of phase change memory elements, respectively.
2. The phase change memory device according to claim 1 , wherein said phase change memory element changes between low-resistance crystalline state and high-resistance amorphous state by heat generated when supplying current to corresponding said second plug and is capable of rewriting data.
3. The phase change memory device according to claim 2 , wherein said plurality of second plugs is arranged along a direction of gate width of said MOS transistor.
4. The phase change memory device according to claim 1 , wherein said plurality of second plugs is arranged along a direction of gate width of said MOS transistor.
5. The phase change memory device according to claim 4 , wherein said plurality of second plugs is arranged so that said phase change memory elements adjacent in a direction of gate width have an offset to each other in a direction of gate length.
6. A phase change memory device, comprising:
a semiconductor substrate;
a MOS transistor disposed at an intersection of a word line and a bit line;
multiple phase change memory elements electrically connected to one diffusion layer of said MOS transistor, for each of which read and write operations can be individually controlled;
a lower electrode structure for electrically connecting each of said multiple phase change memory elements to said one diffusion layer, and
an upper electrode structure including a plurality of element selection lines for supplying current to each of said plurality of phase change memory elements separately.
7. The phase change memory device according to claim 6 , wherein said element selection line is arranged so that an extension direction thereof is parallel to an extension of said bit line on said semiconductor substrate.
8. The phase change memory device according to claim 6 , wherein said upper electrode structure is a multi-layer structure.
9. The phase change memory device according to claim 8 , wherein said lower electrode structure is a multi-layer structure in addition to said upper electrode structure.
10. A phase change memory device, comprising:
a MOS transistor;
a plurality of phase change elements commonly connected to one diffusion layer of said MOS transistor;
a plurality of element selection lines;
a word line connected to a gate of said MOS transistor; and
a bit line connected to another diffusion layer of said MOS transistor,
wherein said plurality of phase change memory elements are respectively connected to different said element selection lines.
11. The phase change memory device according to claim 10 , wherein said word line and said bit line are arranged orthogonal to each other, and said plurality of element selection lines extend in a same direction as said bit line.
12. A device, comprising:
a transistor formed over a semiconductor substrate having a first diffusion layer and a second diffusion layer;
a first insulating film formed over the transistor, the first diffusion layer and the second diffusion layer;
a first conductive plate formed on the first insulating film;
a first conductive plug formed in the first insulating film and extending from the first conductive plate to the first diffusion layer;
a second insulating film formed on the first conductive plate;
a plurality of first phase change materials formed on the second insulating film; and
a plurality of second conductive plugs each formed in the second insulating film and extending through the second insulating film from a corresponding one of the first phase change materials to the first conductive plate.
13. The device according to claim 12 , further comprising:
a third insulating film formed on the second insulating film;
a second phase change material formed on the third insulating film; and
a third conductive plug formed in the second and the third insulating film and extending from the second phase change material to the first conductive plate.
14. The device according to claim 12 , further comprising:
a third insulating film formed on the second insulating film;
a second conductive plate formed on the third insulating film;
a third conductive plug formed in the third insulating film and extending from the second conductive plate to the first conductive plate;
a fourth insulating film formed on the third conductive plate;
a second phase change material formed on the fourth insulating film; and
a fourth conductive plug formed in the fourth insulating film and extending from the second phase change material to the second conductive plate.
15. The device according to claim 12 , further comprising at least one additional conductive plug formed in the first insulating film and extending from the first conductive plate to the first diffusion layer.
16. The device according to claim 12 , further comprising:
a third insulating film formed over the transistor, the first diffusion layer and the second diffusion layer and formed below the first insulating film;
a first conductive film formed on the third insulating film, coupled to the second diffusion layer and elongated along a first direction; and
a plurality of second conductive films each formed on a corresponding one of the first phase change materials and elongated along the first direction.