Semiconductor device structure and methods of forming the same

A method, comprising:

• forming a fin over a substrate;
• forming a gate stack over the fin;
• and
• forming a first gate spacer layer over the gate stack, comprising:
• forming an as deposited layer using an atomic layer deposition process, comprising:
• flowing a silicon source precursor into a process chamber for a first duration;
• flowing a carbon and nitrogen source precursor into the process chamber at for a second duration;
• and
• flowing an oxygen source precursor into the process chamber for a third duration, wherein a ratio of the first duration to the second duration to the third duration ranges between about 1 to 1 to 1.1 and about 1 to 1 to 1.2, and wherein the as deposited layer has a carbon concentration substantially greater than a nitrogen concentration;
• and
• annealing the as deposited layer in an environment including H2O to form the first gate spacer layer, wherein the first gate spacer layer has a carbon concentration substantially greater than a nitrogen concentration.

A method for forming a dielectric layer, comprising:

• flowing a silicon source precursor into a process chamber at a first flow rate ranging from about 0.2 slm to about 0.8 slm for about 15 seconds to about 25 seconds;
• flowing a carbon and nitrogen source precursor into the process chamber at a second flow rate ranging from about 0.2 slm to about 0.8 slm for about 15 seconds to about 25 seconds;
• and
• flowing an oxygen source precursor into the process chamber at a third flow rate ranging from about 2 slm to about 8 slm for about 20 seconds to about 30 seconds, wherein an as deposited layer is formed;
• and
• annealing the as deposited layer in an environment including H2O to form the dielectric layer, wherein the dielectric layer has a ratio of carbon concentration to nitrogen concentration ranging from about two to one to about ten to one.