Memory cell access devices and methods of making the same

Abstract

Planar access transistor devices and recessed access transistor devices used with semiconductor devices may include gate electrodes having materials with multiple work functions, materials that are electrically isolated from each other and supplied with two or more voltage supplies, or materials that create a diode junction within the gate electrode. Access device drivers are also provided which are capable of driving distinct or identical voltages to the gate electrodes.

1 . A gate electrode, comprising: 
 a first gate material having a first work function associated therewith; and    a second gate material having a second work function associated therewith.    
   
   
       2 . The gate electrode of  claim 1 , wherein the first work function associated with the first gate material is different than the second work function associated with the second gate material.  
   
   
       3 . The gate electrode of  claim 1 , further comprising a separator between the first gate material and the second gate material.  
   
   
       4 . The gate electrode of  claim 3 , wherein the separator comprises a material selected from the group consisting of a nitride, an oxide, a silicide, a conductive metal, and a metallic alloy.  
   
   
       5 . The gate electrode of  claim 3 , further comprising a conductive strap in contact with the first gate material and the second gate material.  
   
   
       6 . The gate electrode of  claim 2 , further comprising a trench in a semiconductor substrate, wherein the first gate material and at least a portion of the second gate material are deposited in the trench of the semiconductor substrate.  
   
   
       7 . The gate electrode of  claim 1 , further comprising a conductive material separating the first gate material and the second gate material.  
   
   
       8 . The gate electrode of  claim 7 , wherein the conductive material comprises a material selected from the group consisting of metals, doped silicon, doped polysilicon, and conductive silicon materials.  
   
   
       9 . The gate electrode of  claim 1 , wherein the first gate material is electrically isolated from the second gate material.  
   
   
       10 . The gate electrode of  claim 9 , wherein the first work function is different than the second work function.  
   
   
       11 . The gate electrode of  claim 9 , further comprising at least one additional gate material, wherein the at least one additional gate material is electrically isolated from the first gate material and the second gate material.  
   
   
       12 . The gate electrode of  claim 9 , wherein the first gate material and the second gate material each comprise a material selected from the group consisting of polysilicon, doped polysilicon, silicon, and doped silicon.  
   
   
       13 . The gate electrode of  claim 9 , wherein the first gate material is electrically isolated from the second gate material in a trench of a recessed access device.  
   
   
       14 . The gate electrode of  claim 9 , further comprising an insulator positioned between the first gate material and the second gate material, wherein the insulator provides electrical isolation between the first gate material and the second gate material.  
   
   
       15 . The gate electrode of  claim 14 , wherein the insulator comprises a material selected from the group consisting of silicon nitride, and silicon dioxide.  
   
   
       16 . The gate electrode of  claim 1 , wherein the first gate material comprises an anode and the second gate electrode comprises a cathode.  
   
   
       17 . The gate electrode of  claim 16 , wherein the first gate material is a p-type material.  
   
   
       18 . The gate electrode of  claim 16 , wherein the second gate material is an n-type material.  
   
   
       19 . A planar access device, comprising: 
 a semiconductor substrate;    an oxide layer positioned over the semiconductor substrate;    a first gate material overlying the oxide layer;    a second gate material overlying the oxide layer;    an electrical connection between the first gate material and the second gate material; and    an insulator cap overlying the first gate material and the second gate material.    
   
   
       20 . The planar access device of  claim 19 , further comprising at least two sidewall spacers positioned on the sides of the gate stack and isolating the first gate material and the second gate material between the at least two sidewall spacers and under the insulator cap.  
   
   
       21 . The planar access device of  claim 19 , further comprising a separator positioned between the first gate material and the second gate material.  
   
   
       22 . The planar access device of  claim 19 , wherein the first gate material and the second gate material each contact the oxide layer.  
   
   
       23 . The planar access device of  claim 19 , wherein the first gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       24 . The planar access device of  claim 19 , wherein the second gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       25 . The planar access device of  claim 19 , wherein the first gate material comprises a doped polysilicon material and the second gate material comprises a doped polysilicon material, wherein the first gate material and the second gate material are doped with different dopants.  
   
   
       26 . The planar access device of  claim 19 , wherein the electrical connection comprises a conductive strap in contact with the first gate material and the second gate material.  
   
   
       27 . The planar access device of  claim 26 , wherein the conductive strap comprises a conductive material selected from the group consisting of metal, doped polysilicon, doped silicon, and a metal alloy.  
   
   
       28 . The planar access device of  claim 26 , wherein the conductive strap comprises a conductive strap positioned between the first gate material and the second gate material.  
   
   
       29 . The planar access device of  claim 26 , wherein the conductive strap comprises a conductive strap positioned over the first gate material and the second gate material.  
   
   
       30 . A recessed access device, comprising: 
 a semiconductor substrate;    at least one trench in the semiconductor substrate;    an oxide layer positioned over sidewalls of the at least one trench;    a first gate material in a bottom portion of the at least one trench and overlying at least a portion of the oxide layer;    a second gate material in the at least one trench and overlying the first gate material;    an electrical connection between the first gate material and the second gate material; and    an insulator cap overlying the second gate material.    
   
   
       31 . The recessed access device of  claim 30 , further comprising a metal barrier positioned between the first gate material and the second gate material.  
   
   
       32 . The recessed access device of  claim 30 , wherein the first gate material and the second gate material each contact the oxide layer.  
   
   
       33 . The recessed access device of  claim 30 , wherein the first gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       34 . The recessed access device of  claim 30 , wherein the second gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       35 . The recessed access device of  claim 30 , wherein the first gate material comprises a doped polysilicon material and the second gate material comprises a doped polysilicon material, wherein the first gate material and the second gate material are doped with different dopants.  
   
   
       36 . The recessed access device of  claim 30 , wherein the electrical connection comprises a barrier layer in contact with the first gate material and the second gate material.  
   
   
       37 . The recessed access device of  claim 36 , wherein the barrier layer comprises a material selected from the group consisting of metal, doped polysilicon, doped silicon, and an insulator material.  
   
   
       38 . The recessed access device of  claim 36 , wherein the barrier layer comprises a barrier layer positioned between the first gate material and the second gate material.  
   
   
       39 . A recessed access device, comprising: 
 a semiconductor substrate;    at least one trench in the semiconductor substrate;    an oxide layer positioned over sidewalls of the at least one trench;    a first gate material positioned over at least a portion of the sidewalls of the at least one trench;    a second gate material in the at least one trench and at least partially surrounded by the first gate material; and    an insulator cap overlying the first gate material and the second gate material.    
   
   
       40 . The recessed access device of  claim 39 , wherein the first gate material and the second gate material each contact the oxide layer.  
   
   
       41 . The recessed access device of  claim 39 , wherein the first gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       42 . The recessed access device of  claim 39 , wherein the second gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       43 . The recessed access device of  claim 39 , wherein the first gate material comprises a doped polysilicon material and the second gate material comprises a doped polysilicon material, wherein the first gate material and the second gate material are doped with different dopants.  
   
   
       44 . The recessed access device of  claim 39 , wherein the second gate material comprises a material having a higher work function than the first gate material.  
   
   
       45 . A planar access device, comprising: 
 a semiconductor substrate;    an oxide layer positioned over the semiconductor substrate;    a first gate material overlying the oxide layer;    a second gate material overlying the oxide layer;    an insulator between the first gate material and the second gate material; and    an insulator cap overlying the first gate material and the second gate material.    
   
   
       46 . The planar access device of  claim 45 , further comprising at least two sidewall spacers positioned on sides of the gate stack and isolating the first gate material and the second gate material between the at least two sidewall spacers and under the insulator cap.  
   
   
       47 . The planar access device of  claim 45 , wherein the insulator comprises a material selected from the group consisting of silicon nitride and silicon dioxide.  
   
   
       48 . The planar access device of  claim 45 , wherein the first gate material and the second gate material each contact the oxide layer.  
   
   
       49 . The planar access device of  claim 45 , wherein the first gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       50 . The planar access device of  claim 45 , wherein the second gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       51 . The planar access device of  claim 45 , wherein the first gate material comprises a doped polysilicon material and the second gate material comprises a doped polysilicon material, wherein the first gate material and the second gate material are doped with different dopants.  
   
   
       52 . The planar access device of  claim 45 , further comprising: 
 a first contact between the first gate material and a first voltage supply; and    a second contact between the second gate material and a second voltage supply.    
   
   
       53 . The planar access device of  claim 52 , wherein the first voltage supply and the second voltage supply originate from an access device driver.  
   
   
       54 . The planar access device of  claim 52 , wherein the first voltage supply and the second voltage supply are configured to provide the same or different voltages to the first contact and the second contact.  
   
   
       55 . A recessed access device, comprising: 
 a semiconductor substrate;    at least one trench in the semiconductor substrate;    an oxide layer positioned over sidewalls of the at least one trench;    a first gate material in a bottom portion of the at least one trench and overlying at least a portion of the oxide layer;    an insulator overlying the first gate material;    a second gate material in the at least one trench and overlying the insulator; and    an insulator cap overlying the second gate material.    
   
   
       56 . The recessed access device of  claim 55 , wherein the first gate material and the second gate material each contact the oxide layer.  
   
   
       57 . The recessed access device of  claim 55 , wherein the first gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       58 . The recessed access device of  claim 55 , wherein the second gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, and metal.  
   
   
       59 . The recessed access device of  claim 55 , wherein the first gate material comprises a doped polysilicon material and the second gate material comprises a doped polysilicon material, wherein the first gate material and the second gate material are doped with different dopants.  
   
   
       60 . The recessed access device of  claim 55 , wherein the insulator comprises a material selected from the group consisting of silicon nitride and silicon dioxide.  
   
   
       61 . The recessed access device of  claim 55 , further comprising: 
 a first contact between the first gate material and a first voltage supply; and    a second contact between the second gate material and a second voltage supply.    
   
   
       62 . The recessed access device of  claim 61 , wherein the first voltage supply and the second voltage supply originate from an access device driver.  
   
   
       63 . The recessed access device of  claim 61 , wherein the first voltage supply and the second voltage supply are configured to provide the same or different voltages to the first contact and the second contact.  
   
   
       64 . A planar access device, comprising: 
 a semiconductor substrate;    an oxide layer positioned over the semiconductor substrate;    a cathode gate material overlying the oxide layer;    an anode gate material overlying the oxide layer and positioned next to the cathode gate material, wherein the anode gate material and the cathode gate material form a diode; and    an insulator cap overlying the cathode gate material and the anode gate material.    
   
   
       65 . The planar access device of  claim 64 , further comprising at least two sidewall spacers positioned on sides of the gate stack and isolating the cathode gate material and the anode gate material between the at least two sidewall spacers and under the insulator cap.  
   
   
       66 . The planar access device of  claim 64 , wherein the cathode gate material and the anode gate material each contact the oxide layer.  
   
   
       67 . The planar access device of  claim 64 , wherein the cathode gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, metal, ruthenium-tantalum, and tantalum nitride.  
   
   
       68 . The planar access device of  claim 64 , wherein the anode gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, metal, ruthenium-tantalum, and tantalum nitride.  
   
   
       69 . The planar access device of  claim 64 , wherein the cathode gate material comprises an n-type cathode material.  
   
   
       70 . The planar access device of  claim 64 , wherein the anode gate material comprises a p-type anode material.  
   
   
       71 . The planar access device of  claim 64 , wherein the cathode gate material comprises a doped polysilicon material and the anode gate material comprises a doped polysilicon material, wherein the cathode gate material and the anode gate material are doped with different dopants.  
   
   
       72 . The planar access device of  claim 64 , further comprising: 
 a first contact between the cathode gate material and a first voltage supply; and    a second contact between the anode gate material and a second voltage supply.    
   
   
       73 . The planar access device of  claim 72 , wherein the first voltage supply and the second voltage supply originate from an access device driver.  
   
   
       74 . The planar access device of  claim 72 , wherein the first voltage supply and the second voltage supply are configured to provide the same or different voltages to the first contact and the second contact.  
   
   
       75 . The gate stack of  claim 64 , wherein the diode comprises a Schottky-Barrier diode.  
   
   
       76 . A recessed access device, comprising: 
 a semiconductor substrate;    at least one trench in the semiconductor substrate;    an oxide layer positioned over sidewalls of the at least one trench;    an anode gate material in a bottom portion of the at least one trench and overlying at least a portion of the oxide layer;    a cathode gate material in the at least one trench and overlying the anode gate material, wherein the anode gate material and the cathode gate material form a diode; and    an insulator cap overlying the cathode gate material.    
   
   
       77 . The recessed access device of  claim 76 , wherein the anode gate material and the cathode gate material each contact the oxide layer.  
   
   
       78 . The recessed access device of  claim 76 , wherein the anode gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, metal, ruthenium-tantalum, and tantalum nitride.  
   
   
       79 . The recessed access device of  claim 76 , wherein the cathode gate material comprises a material selected from the group consisting of polysilicon, doped polysilicon, metal, ruthenium-tantalum, and tantalum nitride.  
   
   
       80 . The recessed access device of  claim 76 , wherein the anode gate material comprises a doped polysilicon material and the cathode gate material comprises a doped polysilicon material, wherein the anode gate material and the cathode gate material are doped with different dopants.  
   
   
       81 . The recessed access device of  claim 76 , wherein the cathode gate material comprises an n-type cathode material.  
   
   
       82 . The recessed access device of  claim 76 , wherein the anode gate material comprises a p-type anode material.  
   
   
       83 . The recessed access device of  claim 76 , further comprising: 
 a first contact between the cathode gate material and a first voltage supply; and    a second contact between the anode gate material and a second voltage supply.    
   
   
       84 . The recessed access device of  claim 83 , wherein the first voltage supply and the second voltage supply originate from an access device driver.  
   
   
       85 . The recessed access device of  claim 83 , wherein the first voltage supply and the second voltage supply are configured to provide the same or different voltages to the first contact and the second contact.  
   
   
       86 . The recessed access device of  claim 76 , wherein the diode comprises a Schottky-Barrier diode.  
   
   
       87 . A access device driver, comprising an access device driver capable of supplying at least two voltages to an access device.  
   
   
       88 . The access device driver of  claim 87 , wherein the access device driver comprises the access device driver illustrated in  FIG. 12 .  
   
   
       89 . The access device driver of  claim 87 , wherein the access device driver comprises the access device driver illustrated in  FIG. 13 .  
   
   
       90 . The access device driver of  claim 87 , further comprising a resistor, wherein the resistor is in electrical communication with at least one of the at least two voltages supplied by the access device driver.