Structure and manufacturing method of semiconductor memory device
View Patent ↗A semiconductor memory device having a cross point structure includes a plurality of upper electrodes arranged to extend in one direction, and a plurality of lower electrodes arranged to extend in another direction at a right angle to the one direction of the upper electrodes. Memory materials are provided between the upper electrodes and the lower electrodes for storage of data. The memory materials are made of a perovskite material and arranged at the lower electrodes side of the corresponding upper electrode extending along the corresponding upper electrode.
1. A semiconductor memory device having a cross point structure comprising:
a plurality of upper electrodes arranged to extend in a direction;
a plurality of lower electrodes on a substrate and arranged to extend in a direction substantially at a right angle to the direction of the upper electrodes;
a first insulating material on the substrate and in between the plurality of lower electrodes such that surfaces of the lower electrodes and the first insulating material are substantially coplanar; and
a group of memory materials arranged between the upper electrodes and the surfaces of the lower electrodes and the first insulating material for storage of data,
wherein the memory materials comprise a perovskite material, and
wherein each of the memory materials is disposed at the lower electrodes side of the corresponding upper electrode and extends along the corresponding upper electrode,
wherein each lower electrode spans multiple upper electrodes such that each lower electrode extends beyond a cell region of a memory cell, which is an area defined by a cross-section between the lower electrode and any upper electrode spanned by the lower electrode, and
wherein the memory material does not extend along the lower electrodes.
2. The semiconductor memory device according to claim 1 , wherein a material of the lower electrodes includes a substance for encouraging an epitaxial growth of the perovskite material.
3. The semiconductor memory device according to claim 1 , wherein a material of the lower electrodes includes at least one of a platinum group of rare metals, a group of their alloys, an electrically conductive oxide group of Ir, Ru, Re, and Os, and another electrically conductive oxide group of SRO(SrRuO 3 ), LSCO((LaSr)CoO 3 ), and YBCO(YbBa 2 Cu 3 O 7 ).
4. The semiconductor memory device according to claim 1 , wherein a material of the upper electrodes includes at least one of a platinum group of rare metals, a group of metals Ag, Al, Cu, Ni, Ti, Ta, and their alloys, an electrically conductive oxide group of Ir, Ru, Re, and Os, and another electrically conductive oxide group of SRO(SrRuO 3 ), LSCO((LaSr)CoO 3 ), and YBCO(YbBa 2 Cu 3 O 7 ).
5. The semiconductor memory device according to claim 1 , wherein the perovskite material comprises an oxide composed of at least one of Pr, Ca, La, Sr, Gd, Nd, Bi, Ba, Y, Ce, Pb, Sm, and Dy and at least one of Ta, Ti, Cu, Mn, Cr, Co, Fe, Ni, and Ga.
6. The semiconductor memory device according to claim 5 , wherein
the perovskite material is an oxide expressed by at least one formula (where 0≦X≦1 and 0≦Z<1) selected from
Pr 1-X Ca X [Mn 1-Z M Z ]O 3 (where M is an element selected from a group of Cr, Co, Fe, Ni, and Ga),
La 1-X AE X MnO 3 (where AE is a bivalent alkali earth metal selected from a group of Ca, Sr, Pb, and Ba),
RE 1-X Sr X MnO 3 (where RE is a trivalent rare earth element selected from a group of Sm, La, Pr, Nd, Gd, and Dy),
La 1-X Co X [Mn 1-Z Co Z ]O 3 ,
Gd 1-X Ca X MnO 3 , and
Nd 1-X Gd X MnO 3 .
7. The semiconductor memory device according to claim 1 , wherein a memory cell of the memory device occupies an area substantially equal to 4F 2 , where F is a minimum width of the patterning process.