US Patent No. 9,059,676

SURFACE ACOUSTIC WAVE DEVICE AND ELECTRONIC COMPONENT


Patent No. 9,059,676
Issue Date June 16, 2015
Title Surface Acoustic Wave Device And Electronic Component
Inventorship Kazuhiro Hirota, Saitama (JP)
Atsushi Mori, Saitama (JP)
Assignee NIHON DEMPA KOGYO CO., LTD., Tokyo (JP)

Claim of US Patent No. 9,059,676

1. A surface acoustic wave device utilizing surface acoustic waves including a leaky surface acoustic wave (LSAW) having a
frequency equal to or higher than 2 GHz, the surface acoustic wave comprising:
a piezoelectric substrate, configured such that the surface acoustic wave propagates along an X-axis direction on a lithium
tantalate substrate cut perpendicularly to a Y-axis rotated by 45°to 46° around the crystal X-axis;

an IDT electrode, including:
a pair of busbars, each busbar extends along the propagation direction of the surface acoustic wave, and is made of a conductor
film formed over the piezoelectric substrate in parallel with each other, and

electrode fingers, made of a conductive film and arranged to intersect each other in a comb-tooth shape from one of the busbars
to the opposite busbar; and

a reflector, having:
a pair of reflector busbars, formed over the piezoelectric substrate in parallel with each other, each busbar is provided
in one side and the other side of the IDT electrode in the propagation direction of the surface acoustic wave and extends
along the propagation direction of the surface acoustic wave, and

reflector electrode fingers, formed to connect the reflector busbars to each other,
wherein, a thickness of the conductor film in each of the electrode fingers is set to 7.5% ?to 8% ?, where ? denotes a periodic
length of the IDT electrode fingers, and

a metallization ratio expressed as a value obtained by dividing a width D of the IDT electrode finger by a sum of the width
D of the electrode finger and an interval S between the neighboring IDT electrode fingers

is set to 0.55 to 0.60 in order to suppress a frequency change against a change of the metallization ratio.