Acoustic wave device and module

An acoustic wave device, comprising:

• a support substrate composed of lithium tantalate in multi-polarization condition;
• an element substrate that is provided on an upper face of the support substrate and is composed of lithium tantalate, a lower face of the element substrate being joined to the upper face of the support substrate;
• and
• a comb-like electrode that is provided on an upper face of the element substrate and excites an acoustic wave,
• wherein a linear thermal expansion coefficient of the support substrate in parallel with a propagation direction of the acoustic wave is smaller than a linear thermal expansion coefficient of the support substrate in an X-axis.

An acoustic wave device, comprising:

• a support substrate composed of lithium tantalate in multi-polarization condition;
• an element substrate that is provided on an upper face of the support substrate and is composed of lithium tantalate, a lower face of the element substrate being joined to the upper face of the support substrate;
• and
• a comb-like electrode that is provided on an upper face of the element substrate and excites an acoustic wave,
• wherein a sidewall of the acoustic wave device separated into a chip has no difference in level.

A module, comprising

• an acoustic wave device having a support substrate, an element substrate and a comb-like electrode,
• the support substrate being composed of lithium tantalate in multi-polarization condition,
• the element substrate being provided on an upper face of the support substrate and being composed of lithium tantalate,
• a lower face of the element substrate being joined to the upper face of the support substrate,
• the comb-like electrode being provided on an upper face of the element substrate and exciting an acoustic wave,
• wherein domains that voluntarily polarizes are arrayed in the support substrate in random order.