Method of manufacturing surface acoustic wave device chips

1. A method of manufacturing surface acoustic wave device chips, comprising:

a demarcating step of demarcating a plurality of areas on a wafer by a plurality of crossing projected dicing lines on a face side of the wafer, wherein each of the plurality of areas includes a surface acoustic wave device each having an outer edge and a plurality of electrodes spaced from said outer edge;

a grinding step of grinding a reverse side of the wafer;

a laser beam applying step, performed before or after the grinding step, of applying a laser beam, which has a wavelength with which the wafer is transmittable, to the reverse side of the wafer such that the laser beam is focused at a position within the wafer that is closer to the face side of the wafer than the reverse side of the wafer, the laser beam configured to modify an inside portion of the wafer within said outer edge of each of the surface acoustic wave devices, such that the laser beam applying does not cut the wafer, instead forming a modified layer for diffusing an acoustic wave within each of the surface acoustic wave devices, wherein the modified layer is at the position within the wafer; and

a dividing step, performed after the grinding step and the laser beam applying step, of dividing the wafer along the projected dicing lines into a plurality of the surface acoustic wave device chips, each of said surface acoustic wave device chips including one of said plurality of surface acoustic wave devices.

2. The method according to claim 1 , further comprising:

a polishing step performed after the grinding step and before the dividing step, of polishing the reverse side of the wafer.

3. The method according to claim 1 , wherein each surface acoustic wave device includes a pair of interlocking electrodes.

4. The method according to claim 1 , wherein each surface acoustic wave device includes a pair of interlocking comb-shaped arrays of electrodes.

5. The method according to claim 1 , further comprising applying a protective member to the face side of the wafer.

6. The method according to claim 1 , wherein said plurality of electrodes includes a pair of interlocking comb-shaped arrays of electrodes.

7. A method of manufacturing surface acoustic wave device chips, comprising:

a grinding step of grinding a reverse side of a wafer with a surface acoustic wave device formed in each area demarcated by a plurality of crossing projected dicing lines on a face side of the wafer;

before or after the grinding step, a laser beam applying step of applying a laser beam having a wavelength with which the wafer is transmittable to the reverse side of the wafer such that the laser beam is focused at a position within the wafer, the position being closer to the face side of the wafer than a position corresponding to a reverse side of each of the surface acoustic wave device chips to be produced from the wafer, whereby the laser beam does not cut the wafer, but instead modifies an inside portion of the wafer within the area in which the surface acoustic wave device is formed, thereby forming a modified layer for diffusing an acoustic wave; and

after the grinding step and the laser beam applying step, a dividing step of dividing the wafer along the projected dicing lines into a plurality of the surface acoustic wave device chips to manufacture a plurality of the surface acoustic wave device chips each having the modified layer formed therein for diffusing an acoustic wave.