Surface acoustic wave device and method of producing the same

Abstract

A surface acoustic wave device includes: interdigital transducers; first electrode pads that are connected to the interdigital transducers through wire patterns; and a piezoelectric substrate on which the interdigital transducers, the first electrode pads, and the wire patterns, are formed. In this surface acoustic wave device, at least one of the first electrode pads is not connected to a ground pattern, and the piezoelectric substrate has a conductivity in the range of 10 −12 /Ω·cm to 10 −6 /Ω·cm.

1 . A method of producing a surface acoustic wave device having a piezoelectric substrate on which metal patterns including interdigital transducers and first electrode pads are formed, 
 the method comprising the steps of:    forming the metal patterns on the piezoelectric substrate having a conductivity in the range of 10 −12 /Ω·cm to 10 −6 /Ω·cm; and    bonding a substrate to the piezoelectric substrate, the substrate having second electrode pads aligned to the first electrode pads and a second layer formed in a region corresponding to the first layer, the bonding being performed by joining the first layer and the second layer to each other.    
   
   
       2 . The method as claimed in  claim 1 , wherein the piezoelectric substrate is made of lithium tantalate or lithium niobate.  
   
   
       3 . The method as claimed in  claim 1 , further comprising the step of 
 subjecting joining surfaces of the first layer and the second layer to surface activation treatment,    wherein the first layer and the second layer that have been subjected to the surface activation treatment are joined to each other in the step of bonding.    
   
   
       4 . The method as claimed in  claim 1 , wherein the first layer and the second layer are made of the same metallic material as the first electrode pads and the second electrode pads.  
   
   
       5 . The method as claimed in  claim 1 , wherein: 
 the piezoelectric substrate and the substrate have multiple structures;    the method comprises a step of dividing the piezoelectric substrate and the substrate that have been bonded to each other in the step of bonding into individual devices.