Patent ID: 7888841

Claim:
A boundary acoustic wave device comprising: a LiNbO 3 substrate including a plurality of grooves provided in an upper surface thereof and having Euler angles (0° , θ, −45° to +45°); electrodes defined by metal material filled in the grooves; and a silicon dioxide layer arranged over the LiNbO 3 substrate and the electrodes; wherein the upper surface of the silicon dioxide layer is flat or substantially flat; the metal material defining the electrodes is at least one selected from the group consisting of Al, Ti, Ni, Cr, Cu, W, Ta, Pt, and Ag; Al and Ti are grouped into a first group; Ni and Cr are grouped into a second group; Cu, W, Ta, Pt, and Ag are grouped into a third group; and a thickness of the electrodes made of the metal materials assigned to each group, θ of the Euler angles of the LiNbO 3 substrate, and the thickness of the silicon dioxide layer are within any of the ranges shown in the table below: α ≦ 0.1 θ of Euler angles (0°, θ, −45° to 45°) 0.04 ≦ Thickness of first (0, 76 to 106, 0.8 ≦ Thickness of silicon group electrode < 0.07 −45 to 45) dioxide layer ≦ 2.5 0.07 ≦ Thickness of first (0, 66 to 116, 0.8 ≦ Thickness of silicon group electrode < 0.1 −45 to 45) dioxide layer ≦ 2.5 0.1 ≦ Thickness of first (0, 56 to 125, 0.8 ≦ Thickness of silicon group electrode ≦ 0.2 −45 to 45) dioxide layer ≦ 2.5 0.01 ≦ Thickness of second (0, 71 to 101, 0.8 ≦ Thickness of silicon group electrode < 0.02 −45 to 45) dioxide layer ≦ 3.0 0.02 ≦ Thickness of second (0, 68 to 103, 0.8 ≦ Thickness of silicon group electrode < 0.06 −45 to 45) dioxide layer ≦ 3.0 0.06 ≦ Thickness of second (0, 66 to 109, 0.8 ≦ Thickness of silicon group electrode < 0.08 −45 to 45) dioxide layer ≦ 3.0 0.08 ≦ Thickness of second (0, 61 to 123, 0.8 ≦ Thickness of silicon group electrode ≦ 0.16 −45 to 45) dioxide layer ≦ 3.0 0.01 ≦ Thickness of third (0, 61 to 112, 0.8 ≦ Thickness of silicon group electrode < 0.02 −45 to 45) dioxide layer ≦ 4.0 0.02 ≦ Thickness of third (0, 60 to 122, 0.8 ≦ Thickness of silicon group electrode < 0.06 −45 to 45) dioxide layer ≦ 4.0 0.06 ≦ Thickness of third (0, 56 to 132, 0.8 ≦ Thickness of silicon group electrode < 0.08 −45 to 45) dioxide layer ≦ 4.0 0.08 ≦ Thickness of third (0, 51 to 136, 0.8 ≦ Thickness of silicon group electrode ≦ 0.10 −45 to 45) dioxide layer ≦ 4.0 The thickness of each electrode and the thickness of the silicon dioxide layer are normalized thickness H/λ (λ is the wavelength of a boundary acoustic wave).