Wafer and surface acoustic wave device

A surface acoustic wave device comprising a wafer constructed of a trigonal lanthanum/gallium silicate crystal cut out at predetermined cut angles (.alpha., .beta.), wherein:

• application of a voltage signal of a predetermined level to said wafer permits a surface acoustic wave to be excited in said wafer and propagate in said wafer;
• and
• said wafer, supposing that the trigonal lanthanum/gallium silicate crystal has three crystal axes including an X-axis (electric axis), a Y-axis (mechanical axis) and a Z-axis (optical axis), is cut out so that a normal line (n) on a surface of said wafer has the cut angle .alpha. defined to be 20.degree..ltoreq..alpha..ltoreq.40.degree. with respect to the Y-axis in a counterclockwise direction from the Y-axis in a Y-Z plane and a propagation direction (S) of said surface acoustic wave has the cut angle .alpha. defined to be 35.degree..ltoreq..beta..ltoreq.70.degree. with respect to the X-axis in a counterclockwise direction from the X-axis in the surface of said wafer.

A surface acoustic wave device comprising a wafer constructed of a trigonal lanthanum/gallium silicate crystal cut out at predetermined cut angles (.alpha., .beta.), wherein:

• application of a voltage signal of a predetermined level to said wafer permits a surface acoustic wave to be excited in said wafer and propagate in said wafer;
• and
• said wafer, supposing that the trigonal lanthanum/gallium silicate crystal has three crystal axes including an X-axis, (electric axis), a Y-axis (mechanical axis) and a Z-axis (optical axis), is cut out so that a normal line (n) on a surface of said wafer has the cut angle .alpha. defined to be -1.5.degree..ltoreq..alpha..ltoreq.15.degree. with respect to the Y-axis in a clockwise direction from the Y-axis in a Y-Z, plane and a propagation direction (S) of said surface acoustic wave has the cut angle .beta. defined to be 70.degree..ltoreq..beta..ltoreq.120.degree. with respect to the X-axis in a counterclockwise direction from the X-axis in the surface of said wafer.