Ferroelectric Devices including a Layer having Two or More Stable Configurations

Abstract

Ferroelectric semiconductor devices are provided by including a ferroelectric layer in the device that is made of a material that is not ferroelectric in bulk. Such layers can be disposed at interfaces to promote ferroelectric switching in a semiconductor device. Switching of conduction in the semiconductor is effected by the polarization of a mechanically bi-stable material. This material is not ferroelectric in bulk but can be considered to be when the thickness is sufficiently reduced down to a few atomic layers. Devices including such ferroelectric layers are suitable for various applications, such as transistors and memory cells (both volatile and non-volatile).

1 . Apparatus comprising:
 a semiconductor substrate;   a ferroelectric layer of a material disposed on or above said substrate;   wherein said ferroelectric layer has at least two stable configurations having different electrical polarizations;   wherein said ferroelectric layer can be switched between said stable configurations by an applied electric field; and   wherein said material does not exhibit bulk ferroelectricity.   
     
     
         2 . The apparatus of  claim 1 , wherein said substrate comprises silicon or germanium. 
     
     
         3 . The apparatus of  claim 1 , wherein said material has a composition MX 2 . 
     
     
         4 . The apparatus of  claim 3 , wherein said composition MX 2  has M selected from the group consisting of Zr, Hf, Ce, Ca, Pt, Pd, Rh, Ir, Ti, Fe, Ni, Co and V, and has X selected from the group consisting of O, F, S, As and P. 
     
     
         5 . The apparatus of  claim 4 , wherein said ferroelectric layer comprises a material selected from the group consisting of: zirconium oxide, hafnium oxide, calcium fluoride, cerium oxide and mixtures thereof. 
     
     
         6 . The apparatus of  claim 1 , wherein said ferroelectric layer is disposed on said substrate and further comprising an insulator disposed on a surface of said ferroelectric layer opposite said substrate. 
     
     
         7 . The apparatus of  claim 6 , wherein said insulator comprises a material selected from the group consisting of lead titanate, barium titanate, strontium titanate, and alloys or mixtures thereof. 
     
     
         8 . The apparatus of  claim 7 , wherein said insulator comprises strontium titanate. 
     
     
         9 . The apparatus of  claim 6 , wherein said insulator comprises a material that does not exhibit bulk ferroelectricity, but is ferroelectric when substantially matched in size and symmetry to said substrate. 
     
     
         10 . The apparatus of  claim 6 , wherein said insulator comprises a material that is not ferroelectric. 
     
     
         11 . The apparatus of  claim 6 , wherein said insulator is amorphous. 
     
     
         12 . The apparatus of  claim 1 , further comprising an insulating layer stack disposed on said substrate, wherein said ferroelectric layer is one of the layers of said insulating layer stack. 
     
     
         13 . The apparatus of  claim 1 , wherein said ferroelectric layer is a monolayer. 
     
     
         14 . A semiconductor device including the apparatus of  claim 1 . 
     
     
         15 . The device of  claim 14 , wherein said semiconductor device is selected from the group consisting of: transistors, volatile memory cells, non-volatile memory cells, and combinations thereof.