Fin Field Effect Transistors having Conformal Oxide Layers and Methods of Forming Same

A method comprising:

• forming a first gate dielectric over a top surface and along a sidewall of a first semiconductor fin, the first semiconductor fin extending upwards from a semiconductor substrate, wherein forming the first gate dielectric comprises:
• applying a thermal nitridation process to form a nitride layer over the top surface and the sidewall of the first semiconductor fin;
• and
• after the thermal nitridation process, performing an in-situ steam generation (ISSG) process on the nitride layer;
• forming a first gate structure over the first gate dielectric to provide a first fin field effect transistor (FinFET) having a first operating voltage;
• forming a second gate dielectric over a top surface and along a sidewall of a second semiconductor fin, the second semiconductor fin extending upwards from the semiconductor substrate;
• and
• forming a second gate structure over the second gate dielectric to provide a second finFET having a second operating voltage different than the first operating voltage.

A method comprising:

• forming a first gate dielectric on top surfaces and sidewalls of a first semiconductor fin and a second semiconductor fin, wherein forming the first gate dielectric comprises:
• performing a first nitridation to form a first nitride layer on the top surfaces and the sidewalls of the first semiconductor fin and the second semiconductor fin;
• and
• after performing the first nitridation, performing an in-situ steam generation (ISSG) process on the first nitride layer to form an oxynitride layer;
• masking a first portion of the first gate dielectric on the first semiconductor fin;
• while masking the first portion of the first gate dielectric, replacing a second portion of the first gate dielectric on the second semiconductor fin with a second gate dielectric;
• unmasking the first portion of the first gate dielectric;
• forming a first gate electrode over the first portion of the first gate dielectric to provide a first fin field effect transistor (finFET) having a first operating voltage;
• and
• forming a second gate electrode over the second gate dielectric to provide a second finFET having a second operating voltage less than the first operating voltage.