Abstract: Embodiments described herein provide a method of forming a low-k carbon-doped silicon oxide (CDO) layer having a high hardness by a plasma-enhanced chemical vapor deposition (PECVD) process. The method includes providing a carrier gas at a carrier gas flow rate and a CDO precursor at a precursor flow rate to a process chamber. A radio frequency (RF) power is applied at a power level and a frequency to the CDO precursor. The CDO layer is deposited on a substrate within the process chamber.