ACOUSTIC WAVE DEVICE

PROBLEM TO BE SOLVED: To provide an acoustic wave device capable of improving a gain and accuracy without increasing cost and complicating a configuration significantly, the acoustic wave device being configured to implement measurement or monitoring relating to a desired medium on the basis of a surface acoustic wave propagation property on a piezoelectric substrate.SOLUTION: The acoustic wave device comprises two couples of transmission electrodes and reception electrodes which are disposed on a piezoelectric substrate 21 oppositely to each other with a propagation path 22 interposed therebetween. Between the two couples, a specific couple includes an additional electrode 11 formed on the propagation path for reflecting or absorbing in a predetermined ratio a surface acoustic wave coming from the transmission electrode. The shape, size, thickness, number and arrangement of additional electrodes are entirely or partially set in such a manner that a difference between a phase shift amount of a surface acoustic wave coming to a reception electrode in a specific couple between the two couples and a phase shift amount of a surface acoustic wave individually coming to a reception electrode in the other couple than the specific couple becomes (2n-0.5) radian or (2n+0.5) radian with respect to an integer (n).