Patent attributes
A bulk acoustic wave device includes: a bulk acoustic wave element including a piezoelectric layer formed on a substrate, a lower electrode contacting a lower surface of the piezoelectric layer, and an upper electrode contacting an upper surface of the piezoelectric layer and partially overlapping the lower electrode, a lower hollow section being formed between the substrate and the lower surface of the piezoelectric layer, a first through-hole reaching the lower hollow section being formed through the bulk acoustic wave element in a direction perpendicular to a surface of the piezoelectric layer; an upper hollow section forming layer forming an upper hollow section with the upper surface of the piezoelectric layer, a second through-hole reaching the upper hollow section being formed therethrough in a direction perpendicular to a surface thereof; and a sealing layer covering the upper hollow section forming layer and filling up the second through-hole.
