Vertical transistors with sidewall gate air gaps and methods therefor

1. A method comprising:

forming a first vertically-oriented transistor above a substrate, the first vertically-oriented transistor comprising a first sidewall gate disposed in a first direction;

forming a second vertically-oriented transistor above the substrate, the second vertically-oriented transistor comprising a second sidewall gate disposed in the first direction; and

forming an air gap chamber above the substrate disposed between the first sidewall gate and the second sidewall gate, and extending in the first direction, the air gap chamber comprising an air gap, wherein forming the air gap chamber comprises:

forming a first sidewall liner on the first sidewall gate and a second sidewall liner on the second sidewall gate;

etching a top edge of the first sidewall gate below a top edge of the first sidewall liner; and

etching a top edge of the second sidewall gate below a top edge of the second sidewall liner,

wherein:

the first sidewall liner comprises a first upper section and the second sidewall liner comprises a second upper section; and

the first upper section bends or pitches towards the second upper section.

2. The method of claim 1 , wherein forming the air gap chamber comprises forming a U-shaped channel between the first sidewall gate and the second sidewall gate, the U-shaped channel comprising a material comprising a tensile stress.

3. The method of claim 1 , further comprising substantially enclosing the air gap chamber.

4. The method of claim 1 , wherein the air gap chamber comprises one or more of silicon nitride and silicon oxynitride.

5. The method of claim 1 , wherein forming the first vertically-oriented transistor and the second vertically-oriented transistor comprises:

forming a vertical stack of semiconductor material;

etching the vertical stack of semiconductor material to form a first vertically-oriented transistor pillar and a second vertically-oriented transistor pillar;

forming the first sidewall gate on a first side of the first vertically-oriented transistor pillar; and

forming the second sidewall gate on a first side of the second vertically-oriented transistor pillar.

6. The method of claim 5 , wherein forming a vertical stack of semiconductor material comprises forming a first region having a first conductivity type, a second region having a second conductivity type and a third region having the first conductivity type.

7. The method of claim 1 , wherein:

the first vertically-oriented transistor comprises a first terminal, a second terminal and a third terminal, the second vertically-oriented transistor comprises a first terminal, a second terminal and a third terminal; and

the method further comprises:

coupling the first terminal of the first vertically-oriented transistor to a first vertical bit line of a memory array, coupling the second terminal of the first vertically-oriented transistor to a global bit line of the memory array, and coupling the third terminal of the first vertically-oriented transistor to the first sidewall gate; and

coupling the first terminal of the second vertically-oriented transistor to a second vertical bit line of the memory array, coupling the second terminal of the second vertically-oriented transistor to the global bit line of the memory array, and coupling the third terminal of the second vertically-oriented transistor to the second sidewall gate.

8. The method of claim 7 , wherein memory array comprises a memory cell comprising a vertical strip of non-volatile memory material.

9. The method of claim 8 , wherein the nonvolatile memory material comprises one or more of HfO 2 , Al 2 O 3 , HfSiO x , HfSiO x N y , HfAlO x , Nb 2 O 5 , Ta 2 O 5 , ZrO 2 , Cr 2 O 3 , Fe 2 O 3 , Ni 2 O 3 , Co 2 O 3 , WO 3 , TiO 2 , SrZrO 3 , SrTiO 3 .