Multiple thickness gate dielectrics for replacement gate field effect transistors
After removal of the disposable gate structures to form gate cavities in a planarization dielectric layer, a silicon oxide layer is conformally deposited on silicon-oxide-based gate dielectric portions in the gate cavities. A portion of the silicon oxide layer can be nitridated to form a silicon oxynitride layer. A patterned masking material layer can be employed to physically expose a semiconductor surface from a first-type gate cavity. The silicon oxide layer can be removed while preserving an underlying silicon-oxide-based gate dielectric portion in a second-type gate cavity. A stack of a silicon oxynitride layer and an underlying silicon-oxide-based gate dielectric can be protected by a patterned masking material layer in a third-type gate cavity during removal of the silicon oxide layer in the second-type gate cavity. A high dielectric constant gate dielectric layer can be formed in the gate cavities to provide gate dielectrics of different types.
1. A semiconductor structure comprising:
a gate dielectric comprising a chemical oxide layer contacting a first surface of a semiconductor substrate and a U-shaped gate dielectric portion comprising a high dielectric constant (high-k) gate dielectric material contacting said chemical oxide layer; and
another gate dielectric comprising a semiconductor oxide-based dielectric portion and contacting a second surface of said semiconductor substrate, a U-shaped silicon oxynitride layer contacting said semiconductor oxide-based dielectric portion, and another U-shaped gate dielectric portion contacting inner sidewalls of said U-shaped silicon oxynitride layer.
2. The semiconductor structure of claim 1 , wherein said U-shaped gate dielectric portion and said another U-shaped gate dielectric portion have a same composition and a same thickness.
3. The semiconductor structure of claim 1 , wherein said chemical oxide layer has a thickness in a range from 0.2 nm to 0.6 nm, and said semiconductor oxide-based dielectric portion has a thickness in a range from 1.5 nm to 10 nm.
4. The semiconductor structure of claim 1 , wherein said U-shaped silicon oxynitride layer is a conformal layer having a same thickness throughout an entirety thereof, wherein said same thickness is in a range from 0.6 nm to 1.5 nm.
5. The semiconductor structure of claim 1 , wherein said U-shaped gate dielectric portion and said another U-shaped gate dielectric portion comprise a dielectric metal oxide having a dielectric constant greater than 8.0.
6. The semiconductor structure of claim 1 , further comprising:
a gate electrode contacting inner sidewalls of said U-shaped gate dielectric portion; and
another gate electrode contacting inner sidewalls of said another U-shaped gate dielectric portion.
7. The semiconductor structure of claim 1 , further comprising:
a gate spacer contacting outer sidewalls of vertical portions of said U-shaped gate dielectric portion; and
another gate spacer contacting outer sidewalls of vertical portions of said U-shaped silicon oxynitride layer.
8. The semiconductor structure of claim 1 , further comprising yet another gate dielectric comprising another semiconductor oxide-based dielectric portion and contacting a third surface of said semiconductor substrate, and yet another U-shaped gate dielectric portion contacting said another semiconductor oxide-based dielectric portion.
9. The semiconductor structure of claim 8 , wherein said U-shaped gate dielectric portion, said another U-shaped gate dielectric portion, and said yet another U-shaped gate dielectric portion have a same composition and a same thickness.
10. The semiconductor structure of claim 1 , further comprising yet another gate dielectric comprising another semiconductor oxide-based dielectric portion and contacting a third surface of said semiconductor substrate, a U-shaped silicon oxide layer contacting said another silicon-oxide based dielectric portion, and yet another U-shaped gate dielectric portion contacting inner sidewalls of said U-shaped silicon oxide layer.