An atomic layer deposition (ALD) technique is used to deposit one or more layers on hard mask layers and the sidewalls of low-K dielectric trench as part of the trench etch process. The ALD layer(s) can prevent the hard mask from being eroded during various hard mask open processes. Further, the ALD layer(s) may be utilized to prevent the low-K dielectric sidewall from being laterally etched during the low-K dielectric trench etch. Hence, better control of the trench profile and better critical dimension control may be provided.