Semiconductor device structures having dielectric features and methods of forming dielectric features are described herein. In some examples, the dielectric features are formed by an ALD process followed by a varying temperature anneal process. The dielectric features can have high density, low carbon concentration, and lower k-value. The dielectric features formed according to the present disclosure has improved resistance against etching chemistry, plasma damage, and physical bombardment in subsequent processes while maintaining a lower k-value for target capacitance efficiency.