Resonator, apparatus having the same and fabrication method of resonator

摘要

A resonator includes a substrate, and a resonating unit formed on the substrate, and having a lower electrode, a piezoelectric film, and an upper electrode. The lower electrode is formed of at least two layers to adjust a piezoelectric coupling coefficient. The lower electrode includes a first electrode layer and a second electrode layer, which have crystallographic characteristics, particularly, grain sizes or surface roughnesses Ra, different from each other, respectively. The first and the second electrode layers are formed to have a predetermined thickness ratio to each other.