Abstract: An inductively coupled plasma dry etch process can obtain a deep etching profile in a piezoelectric material, such as lithium niobate, with minimum roughness and substantially vertical sidewalls. In addition, quality metal masks can be achieved by employing a hydrogen-plasma treatment prior to the processing steps. Periodic interruption steps can be included in the plasma dry etch procedure followed by a chemical cleaning between each cycle to avoid thermal effect and minimize byproduct redeposition during the long etching process. A deep etching profile in a piezoelectric material, such as a ScxAl1-xN film, can be attained with minimum roughness and substantially vertical sidewalls using wet etching and a patterned mask, where the patterned mask is formed using another mask.