Resistive memory cells and devices having asymmetrical contacts

Abstract

A memory cell includes a plug-type first electrode in a substrate, a magneto-resistive memory element disposed on the first electrode, and a second electrode disposed on the magneto-resistive memory element opposite the first electrode. The second electrode has an area of overlap with the magneto-resistive memory element that is greater than an area of overlap of the first electrode and the magneto-resistive memory element. The first surface may, for example, be substantially circular and have a diameter less than a minimum planar dimension (e.g., width) of the second surface. The magneto-resistive memory element may include a colossal magneto-resistive material, such as an insulating material with a perovskite phase and/or a transition metal oxide.

1 . A memory cell comprising:
 a plug-type first electrode in a substrate;   a transition metal oxide resistive memory element film disposed on the first electrode; and   a second electrode disposed on the resistive memory element film opposite the first electrode, the second electrode having an area of overlap with the transition metal oxide resistive memory element film that is greater than an area of overlap of the first electrode and the transition metal oxide resistive memory element film.   
     
     
         2 . The memory cell of  claim 1 , wherein the area of overlap of the first electrode is substantially circular and has a diameter less than a minimum dimension of the area of overlap of the second electrode. 
     
     
         3 . The memory cell of  claim 1 , wherein the transition metal oxide resistive memory element film comprises a layer pattern having a minimum planar dimension that is less than a minimum planar dimension of the second electrode. 
     
     
         4 . The memory cell of  claim 1 , wherein the first electrode is disposed in an insulating layer and an insulating spacer is disposed between the first electrode and the insulating layer. 
     
     
         5 . The memory cell of  claim 4 , wherein the first electrode partially fills a contact hole in the insulating layer, and wherein the transition metal oxide resistive memory element film extends into the contact hole to contact the first electrode. 
     
     
         6 . The memory cell of  claim 1 , further comprising a conductive line electrically connected to the plug-type first electrode and disposed under the plug-type first electrode, wherein the conductive line is transverse to the second electrode. 
     
     
         7 . The memory cell of  claim 1 , wherein the transition metal oxide resistive memory element film comprises a transition metal oxide with the formula MO x , wherein M is nickel (Ni), cobalt (Co), zinc (Zn) or copper (Cu), and wherein x is in a range from about 0.5 to about 0.99. 
     
     
         8 . The memory cell of  claim 1 , wherein the transition metal oxide resistive memory element film comprises a transition metal oxide with the formula MO x , wherein M is hafnium (Hf), zirconium (Zr), titanium (Ti) or chromium (Cr), and wherein x is in a range from about 1.0 to about 1.98. 
     
     
         9 . The memory cell of  claim 1 , wherein the transition metal oxide resistive memory element film comprises a transition metal with the formula MO x , wherein M is iron (Fe) and wherein x is in a range from about 0.75 to about 1.485. 
     
     
         10 . The memory cell of  claim 1 , wherein the transition metal oxide resistive memory element film comprises a transition metal oxide with the formula MO x , wherein M is niobium (Nb) and wherein x is in a range from about 1.25 to about 2.475. 
     
     
         11 . The memory cell of  claim 1 , wherein the first electrode comprises iridium (Ir), platinum (Pt), ruthenium (Ru), polycrystalline silicon, tungsten (W), titanium nitride (TiN) and/or titanium aluminum nitride (TiAlN). 
     
     
         12 . The memory cell of  claim 1 , wherein the first electrode comprises tungsten, wherein the second electrode comprises iridium and wherein the transition metal oxide resistive memory element film comprises nickel oxide.