Abstract: An acoustic wave resonator includes: an IDT located on a piezoelectric substrate, including comb-shaped electrodes facing each other and including electrode fingers and a bus bar connecting the electrode fingers; a first silicon oxide film located on the electrode fingers in an overlap region where the electrode fingers overlap and having a film thickness in a part of edge regions, which correspond to both ends of the overlap region, equal to or less than that in a center region sandwiched between the edge regions; and a second silicon oxide film located on the electrode fingers, containing an element slowing an acoustic velocity in a silicon oxide film when being added to the silicon oxide film, having a concentration of the element greater than that in the first silicon oxide film, and having a film thickness in a part of the edge regions greater than that in the center region.

Abstract: An acoustic wave device fabrication method includes: forming on a piezoelectric substrate a comb-shaped electrode and a wiring layer coupled to the comb-shaped electrode; forming on the piezoelectric substrate a first dielectric film having a film thickness greater than those of the comb-shaped electrode and the wiring layer, covering the comb-shaped electrode and the wiring layer, and being made of silicon oxide doped with an element or undoped silicon oxide; forming on the first dielectric film a second dielectric film having an aperture above the wiring layer; removing the first dielectric film exposed by the aperture of the second dielectric film by wet etching using an etching liquid causing an etching rate of the second dielectric film to be less than that of the first dielectric film so that the first dielectric film is left so as to cover an end face of the wiring layer and the comb-shaped electrode.

Abstract: An acoustic wave device includes: a piezoelectric substrate; a comb-shaped electrode that is located on the piezoelectric substrate and excites an acoustic wave; and a silicon oxide film that is located on the piezoelectric substrate so as to cover the comb-shaped electrode, and has a total concentration of carbon (C), hydrogen (H), nitrogen (N), and fluorine (F) equal to or less than 3.5 atomic %.

Abstract: An acoustic wave resonator includes: a piezoelectric substrate; an IDT located on the piezoelectric substrate and including comb-shaped electrodes facing each other, each of the comb-shaped electrodes including: electrode fingers exciting an acoustic wave; and a bus bar to which the electrode fingers are connected; a dielectric film located on the piezoelectric substrate in an overlap region, where the electrode fingers of one of the comb-shaped electrodes and the electrode fingers of the other overlap, so as to cover the electrode fingers; and an additional film located on the dielectric film in the overlap region and having a density greater than that of the dielectric film, and of which a film thickness in edge regions corresponding to both edges of the overlap region in an extension direction of the electrode fingers is greater than a film thickness in a central region sandwiched between the edge regions in the overlap region.

Abstract: An acoustic wave resonator includes: an IDT located on a piezoelectric substrate, including comb-shaped electrodes facing each other and including electrode fingers and a bus bar connecting the electrode fingers; a first silicon oxide film located on the electrode fingers in an overlap region where the electrode fingers overlap and having a film thickness in a part of edge regions, which correspond to both ends of the overlap region, equal to or less than that in a center region sandwiched between the edge regions; and a second silicon oxide film located on the electrode fingers, containing an element slowing an acoustic velocity in a silicon oxide film when being added to the silicon oxide film, having a concentration of the element greater than that in the first silicon oxide film, and having a film thickness in a part of the edge regions greater than that in the center region.

Abstract: An acoustic wave device fabrication method includes: forming on a piezoelectric substrate a comb-shaped electrode and a wiring layer coupled to the comb-shaped electrode; forming on the piezoelectric substrate a first dielectric film having a film thickness greater than those of the comb-shaped electrode and the wiring layer, covering the comb-shaped electrode and the wiring layer, and being made of silicon oxide doped with an element or undoped silicon oxide; forming on the first dielectric film a second dielectric film having an aperture above the wiring layer; removing the first dielectric film exposed by the aperture of the second dielectric film by wet etching using an etching liquid causing an etching rate of the second dielectric film to be less than that of the first dielectric film so that the first dielectric film is left so as to cover an end face of the wiring layer and the comb-shaped electrode.

Abstract: An acoustic wave resonator includes: a piezoelectric substrate; an IDT located on the piezoelectric substrate and including comb-shaped electrodes facing each other, each of the comb-shaped electrodes including: electrode fingers exciting an acoustic wave; and a bus bar to which the electrode fingers are connected; a dielectric film located on the piezoelectric substrate in an overlap region, where the electrode fingers of one of the comb-shaped electrodes and the electrode fingers of the other overlap, so as to cover the electrode fingers; and an additional film located on the dielectric film in the overlap region and having a density greater than that of the dielectric film, and of which a film thickness in edge regions corresponding to both edges of the overlap region in an extension direction of the electrode fingers is greater than a film thickness in a central region sandwiched between the edge regions in the overlap region.

Abstract: An acoustic wave device includes: a piezoelectric substrate; a comb-shaped electrode that is located on the piezoelectric substrate and excites an acoustic wave; and a silicon oxide film that is located on the piezoelectric substrate so as to cover the comb-shaped electrode, and has a total concentration of carbon (C), hydrogen (H), nitrogen (N), and fluorine (F) equal to or less than 3.5 atomic %.