A piezoelectric resonator element includes a base portion formed of a piezoelectric material, a plurality of resonating arms formed integrally with the base portion and extending parallel to each other, a longitudinal groove formed along a longitudinal direction of each of the resonating arms, and an electrode for driving formed in the longitudinal groove. Reduced levels of scratching, abrasion, wear and particulate generation are achieved by improved smoothing and flattening of the surface and, in a preferred embodiment, through the application of an ion beam assisted diamond-like-carbon film coating deposition. Of course, other claims and combinations are disclosed.