Vertical field effect transistors with self aligned gate and source/drain contacts

1. A method of forming a semiconductor device, the method comprising:

forming a bottom source or drain (S/D) layer on a substrate;

forming a bottom spacer layer on the bottom S/D layer;

forming a vertical transistor channel on the bottom S/D layer, the vertical transistor channel passing through the bottom spacer layer;

forming a high-k metal gate layer on sides of the vertical transistor channel and above the bottom S/D layer;

forming a gate spacer on sides of the vertical transistor channel and on top of the high-k metal gate layer;

removing portions of the high-k metal gate layer with a timed etch;

covering the high-k metal gate layer, the vertical transistor channel and bottom S/D layer with an interlayer dielectric (ILD);

forming with a non-self-aligned contact (SAC) etch a bottom S/D recess through the ILD to expose the bottom S/D layer, the etch removing at least portion of the gate spacer and the high-k metal gate layer;

forming a bottom S/D contact spacer on sides of the bottom S/D recess; and

forming a bottom S/D contact in the bottom S/D recess.

2. The method of claim 1 , wherein forming the bottom S/D recess reduces a thickness of the high-k metal gate layer from a first thickness (t) to a second, smaller thickness (t 2 ).

3. The method of claim 1 , wherein forming the bottom S/D recess reduces a thickness of the gate spacer from a first thickness (gst) to a second, smaller thickness (gst 2 ).

4. The method of claim 1 , wherein a thickness of the bottom S/D contact spacer layer defines a distance (L 1 ) between the bottom S/D contact and the high-k metal gate layer.

5. The method of claim 1 further comprising forming a silicon nitride layer on a top of the vertical transistor channel before removing portions of the high-k metal gate layer.

6. The method of claim 5 further comprising:

removing the silicon nitride layer after the ILD is deposited; and

forming a top S/D layer on top of the vertical transistor channel.

7. The method of claim 6 further comprising:

forming a metallization layer on top of the top S/D layer;

forming a nitride cap over the metallization layer; and

forming an oxide layer over the nitride cap.

8. The method of claim 1 further comprising:

forming a gate contact that passes through the oxide layer and is separated from the top S/D layer by a distance L 2 that is equal to a first thickness (gst) of the gate spacer.

9. A method of forming a semiconductor device, the method comprising:

forming a bottom source or drain (S/D) layer on a substrate;

forming a bottom spacer layer on the bottom source/drain (S/D) layer;

forming a vertical transistor channel on the bottom S/D layer, the vertical transistor passing through the bottom spacer layer;

forming high-k metal gate layer on sides of the vertical transistor channel and above the bottom S/D layer;

forming a silicon nitride layer on a top of the vertical transistor channel before removing portions of the high-k metal gate layer;

forming a gate spacer on sides of the vertical transistor channel and on top of the high-k metal gate layer;

removing portions of the high-k metal gate layer with a timed etch;

covering the high-k metal gate layer, the vertical transistor channel and bottom S/D layer with an interlayer dielectric (ILD);

removing the silicon nitride layer after the ILD is deposited;

forming a top S/D layer on top of the vertical transistor channel;

forming a metallization layer on top of the top S/D layer;

forming a nitride cap over the metallization layer;

adding an oxide layer over the ILD;

removing, with a self-aligned contact (SAC) etch, portions of the ILD and the oxide layer to form a gate contact recess; and

forming a gate contact in the gate contact recess that passes through the oxide layer and is separated from the top S/D layer by a distance L 2 that is equal to a first thickness (gst) of the gate spacer.

10. The method of claim 9 , wherein the SAC etch does not remove the gate spacer.

11. The method of claim 9 further comprising forming with a non-self-aligned contact (SAC) etch a bottom S/D recess through the ILD to expose the bottom S/D layer, the etch removing at least portion of the gate spacer and the high-k metal gate layer.

12. The method of claim 11 further comprising:

forming a bottom S/D contact spacer on sides of the bottom S/D recess; and

forming a bottom S/D contact in the bottom S/D recess.

13. The method of claim 12 further composing:

forming with a non-self-aligned contact (SAC) etch a bottom S/D recess through the interlayer dielectric to expose the bottom S/D layer, the etch removing at least portion of the gate spacer and the high-k metal gate layer;

forming a bottom S/D contact spacer on sides of the bottom S/D recess; and

forming a bottom S/D contact in the bottom S/D recess.

14. The method of claim 13 , wherein forming the bottom S/D recess reduces a thickness of the high-k metal gate layer from a first thickness (t) to a second, smaller thickness (t 2 ).

15. The method of claim 14 , wherein forming the bottom S/D recess reduces a thickness of the gate spacer adjacent the bottom S/D recess from a first thickness (gst) to a second, smaller thickness (gst 2 ).

16. The method of claim 15 , wherein a thickness of the bottom S/D contact spacer layer defines a distance (L 1 ) between the bottom S/D contact and the high-k metal gate layer.

17. A method of forming a complementary metal oxide semiconductor field effect transistor (MOSFET) device having an nFET region and a pFET region, the method comprising:

forming a bottom source/drain (S/D) layer on a substrate;

forming a bottom spacer layer on the bottom source or drain (S/D) layer;

forming an nFET vertical transistor channel and a pFET vertical channel on the bottom S/D layer, the nFET and pFET vertical transistor channels passing through the bottom spacer layer;

forming high-k metal gate layer on sides of the nFET and pFET vertical transistor channels and above the bottom S/D layer;

forming a gate spacer on sides of the nFET and pFET vertical transistor channels and on top of the high-k metal gate layer;

removing portions of the high-k metal gate layer with a timed etch;

covering the high-k metal gate layer, the nFET and pFET vertical transistor channels and bottom S/D layer with an interlayer dielectric (ILD);

forming with a non-self-aligned contact (SAC) etch an nFET bottom S/D recess and a pFET bottom S/D recess through the interlayer dielectric to expose the bottom S/D layer in the nFET region and the pFET region, the etch removing at least portion of the gate spacer and the high-k metal gate layer in both the nFET region and the pFET region;

forming an nFET bottom S/D contact spacer on sides of the bottom S/D recess in the nFET region;

forming a pFET bottom S/D contact spacer on sides of the bottom S/D recess in the pFET region;

filling the bottom S/D recess in the nFET region and the bottom S/D recess in the pFET region with an oxide, the oxide cover ILD layer over the nFET and pFET vertical transistor channels;

removing, with a self-aligned contact (SAC) etch, portions of the ILD and the oxide layer to form a gate contact recess between the nFET and pFET vertical transistor channels;

forming a gate contact that passes through the oxide layer and is separated from the top S/D layer by a distance L 2 that is equal to a first thickness (gst) of the gate spacer;

forming an nFET bottom S/D contact in the nFET bottom S/D recess; and

forming a pFET bottom S/D contact in the pFET bottom S/D recess.

18. The method of claim 7 , wherein forming the nFET bottom S/D recess and the pFET bottom S/D recess reduces a thickness of the high-k metal gate layer in both recesses from a first thickness (t) to a second, smaller thickness (t 2 ).

19. The method of claim 1 , wherein the nFET bottom S/D recess and the pFET bottom S/D recess reduces a thickness of the gate spacer in both recesses from a first thickness (gst) to a second, smaller thickness (gst 2 ).

20. The method of claim 17 , wherein the high-k metal gate layer includes two or more layers.