Abstract: Disclosed herein is a gas distribution plate for use in a gas distribution assembly for a processing chamber, where the gas distribution plate is fabricated from a solid yttrium oxide-comprising substrate, which may also include aluminum oxide. The gas distribution plate includes a plurality of through-holes, which are typically crescent-shaped. Through-holes which have been formed in the solid yttrium oxide-comprising substrate by ultrasonic drilling perform particularly well. The solid yttrium oxide-comprising substrate typically comprises at least 99.9% yttrium oxide, and has a density of at least 4.92 g/cm3, a water absorbency of about 0.02% or less, and an average grain size within the range of about 10 ?m to about 25 ?m. Also disclosed herein are methods for fabricating and cleaning the yttrium oxide-comprising gas distribution plate.