Nonvolatile memory with backplate

Abstract

The present invention provides a non-volatile memory string having serially connected dual-gate devices, in which a first gate dielectric layer adjacent a first gate electrode layer in each dual-gate device is charge-storing and in which the second gate electrode adjacent a non-charge storing gate dielectric layer are connected in common. In one implementation, the second gate electrodes of the dual-gate devices in the memory string are provided by a continuous layer of doped polysilicon, tungsten, tantalum nitride, tungsten nitride or any combination of two or more of these conductors.

1 . A method in a NAND-type non-volatile memory string, comprising:
 Serially connecting a plurality of dual-gate devices, wherein each dual-gate device having a first gate dielectric layer provided between a first gate electrode and a lightly doped channel region and a second gate dielectric layer provided between the lightly doped channel region and a second gate electrode and wherein the first gate dielectric layer is charge-storing; and   providing the second gate electrodes as a continuous layer conducting material.   
   
   
       2 . A method as in  claim 1 , further comprising providing the first gate dielectric layer as stacked layers of materials. 
   
   
       3 . A method as in  claim 2  wherein the materials comprise a selected charge-storing material between silicon oxide layers. 
   
   
       4 . A method as in  claim 3  wherein the charge-storing material comprises one or more of: silicon nitride, silicon oxynitride, a graded layer of silicon nitride with spatial variations in oxygen content, nanocrystals of silicon, germanium, tungsten or another metal, aluminum oxide, or a High-K material. 
   
   
       5 . A method as in  claim 1 , wherein the first gate electrode comprises doped polysilicon, tungsten, tantalum nitride, tungsten nitride or any combination of two or more these conductors.