A method used in fabrication of integrated circuitry comprises forming metal material outwardly of a substrate. At least a majority (i.e., up to and including 100%) of the metal material contains ruthenium in at least one of elemental-form, metal compound-form, or alloy-form. A masking material is formed outwardly of the ruthenium-containing metal material. The masking material comprises at least one of nine specifically enumerated materials or category of materials. The masking material is used as a mask while etching through an exposed portion of the ruthenium-containing metal material to form a feature of integrated circuitry that comprises the ruthenium-containing metal material.