III-V semiconductor device having self-aligned contacts

1. A method comprising:

forming a pair of inner spacers along a vertical sidewall of a gate trench, the gate trench extending from a top surface of a first dielectric layer down to a channel layer of a III-V compound semiconductor-containing heterostructure, the first dielectric layer is above the III-V compound semiconductor-containing heterostructure;

forming a gate conductor within the gate trench;

removing a portion of the first dielectric layer selective to the gate conductor, the pair of inner spacers, and the III-V compound semiconductor-containing heterostructure;

forming a pair of outer spacers adjacent to the pair of inner spacers and above the III-V compound semiconductor-containing heterostructure, the outer spacers are in direct contact with and self-aligned to the inner spacers; and

forming a pair of source-drain contacts within an uppermost layer of the III-V compound semiconductor-containing heterostructure, the pair of source-drain contacts are self-aligned to the pair of outer spacers such that an edge of each individual source-drain contact is aligned with an outside edge of each individual outer spacer.

2. The method of claim 1 , wherein forming a III-V compound semiconductor-containing heterostructure comprises:

forming a III-V compound semiconductor buffer layer on an upper surface of a substrate;

forming a III-V compound semiconductor channel layer on an upper surface of the III-V compound semiconductor buffer layer;

forming a III-V compound semiconductor barrier layer on an upper surface of the III-V compound semiconductor channel layer; and

forming a III-V compound semiconductor cap layer on an upper surface of the III-V compound semiconductor barrier layer.

3. The method of claim 1 , further comprises:

doping a region of the III-V compound semiconductor-containing heterostructure with an element from Group IV, II, or VI of the Periodic Table of Elements.

4. The method of claim 1 , wherein the first dielectric layer comprises a dielectric material having positive etch selectivity from a dielectric material of the pair of inner spacers.

5. The method of claim 1 , wherein forming a pair of source-drain contacts within the III-V compound semiconductor-containing heterostructure comprises:

depositing a blanket layer of metal on top of the III-V compound semiconductor-containing heterostructure;

annealing the blanket layer of metal and the III-V compound semiconductor-containing heterostructure causing the blanket layer of metal to react with an upper layer of the III-V compound semiconductor-containing heterostructure, and form the pair of source-drain contacts; and

removing a unreacted portion of the blanket layer of metal.

6. The method of claim 1 , further comprising:

forming an isolation region, the isolation region separating the gate conductor and the source-drain contacts from an adjacent gate conductor or an adjacent source-drain contact.

7. The method of claim 6 , further comprising:

forming a pair of parasitic spacers in direct contact with and self-aligned to the isolation region, the parasitic spacers are formed simultaneously with the outer spacers.

8. The method of claim 6 , further comprising:

forming a second dielectric layer above the first dielectric layer and above the isolation region.

9. A method comprising:

forming a first dielectric layer on top of a III-V compound semiconductor-containing heterostructure;

forming an isolation region in the first dielectric layer and in the III-V compound semiconductor-containing heterostructure, the isolation at least partially surrounds an active region within the III-V compound semiconductor-containing heterostructure;

forming a gate trench in the active region of the III-V compound semiconductor-containing heterostructure, the gate trench extending from a top surface of the first dielectric layer down to a channel layer of the III-V compound semiconductor-containing heterostructure;

forming a pair of inner spacers along a vertical sidewall of the gate trench;

forming a gate dielectric and a gate conductor within the gate trench, the gate conductor is located on top of the gate dielectric;

removing a portion of the first dielectric layer selective to the gate conductor, the gate dielectric, the pair of inner spacers, and the III-V compound semiconductor-containing heterostructure;

forming a pair of outer spacers adjacent to the pair of inner spacers and above the III-V compound semiconductor-containing heterostructure, the outer spacers are in direct contact with and self-aligned to the inner spacers; and

forming a pair of source-drain contacts within an uppermost layer of the III-V compound semiconductor-containing heterostructure, the pair of source-drain contacts are self-aligned to the pair of outer spacers such that an edge of each individual source-drain contact is aligned with an outside edge of each individual outer spacer.

10. The method of claim 9 , further comprising:

forming a pair of parasitic spacers adjacent to and self-aligned to the isolation region, the parasitic spacers are formed simultaneously with the outer spacers.

11. The method of claim 10 , further comprising:

forming a second dielectric layer above the first dielectric layer and above the isolation region.

12. The method of claim 9 , further comprises:

doping a region of the III-V compound semiconductor-containing heterostructure with an element from Group IV, II, or VI of the Periodic Table of Elements.

13. The method of claim 11 , wherein both the first dielectric layer and the second dielectric layer each comprise a dielectric material having positive etch selectivity from a dielectric material of the pair of inner spacers.