Surface acoustic wave element

A surface acoustic wave element comprising:

• a hard layer essentially consisting of diamond;
• a piezoelectric layer formed directly on said hard layer;
• a silicon dioxide layer formed directly on said piezoelectric layer;
• and an electrode group sandwiched between said hard layer and said piezoelectric layer or between said piezoelectric layer and said silicon dioxide layer, for performing electro-mechanical conversion;
• wherein said piezoelectric layer essentially consists of ZnO and has a thickness Hz, and said silicon dioxide layer has a thickness Hs, such that the ratios 2 .pi.Hz/.lambda. and 2 .pi.Hz/.lambda., where .lambda. denotes a wavelength of said acoustic wave element in the first-order mode, are in a range wherein a propagation velocity v of said acoustic wave element is between about 8,000 m/s and about 10,000 m/s and a temperature coefficient .sigma. of said acoustic wave element is about 0.+-.10 ppm/.degree. C.

A surface acoustic wave element comprising:

• a hard layer essentially consisting of diamond-like carbon film;
• a piezoelectric layer formed directly on said hard layer;
• a silicon dioxide layer formed directly on said piezoelectric layer;
• and an electrode group sandwiched between said hard layer and said piezoelectric layer or between said piezoelectric layer and said silicon dioxide layer, for performing electro-mechanical conversion;
• wherein said piezoelectric layer essentially consists of ZnO, and said hard layer has a thickness Hd such that 3<2 .pi.Hd/.lambda., where .lambda. denotes a wavelength of said acoustic wave element in the first-order mode.

A surface acoustic wave element comprising:

• a hard layer essentially consisting of diamond-like carbon film;
• a piezoelectric layer formed directly on said hard layer;
• a silicon dioxide layer formed directly on said piezoelectric layer;
• and an electrode group sandwiched between said hard layer and said piezoelectric layer or between said piezoelectric layer and said silicon dioxide layer, for performing electro-mechanical conversion;
• wherein said piezoelectric layer essentially consists of ZnO and has a thickness Hz, and said silicon dioxide layer has a thickness Hs, such that the ratios 2 .pi.Hz/.lambda. and 2 .pi.Hz/.lambda., where .lambda. denotes a wavelength of said acoustic wave element in the first-order mode, are in a range wherein a propagation velocity v of said acoustic wave element is between about 8,000 m/s and about 10,000 m/s and a temperature coefficient .sigma. of said acoustic wave element is about 0.+-.10 ppm/.degree. C.

A surface acoustic wave element comprising:

• a hard layer essentially consisting of diamond and a diamond-like carbon film;
• a piezoelectric layer formed directly on said hard layer;
• a silicon dioxide layer formed directly on said piezoelectric layer;
• and an electrode group sandwiched between said hard layer and said piezoelectric layer or between said piezoelectric layer and said silicon dioxide layer, for performing electro-mechanical conversion;
• wherein said piezoelectric layer essentially consists of ZnO, and said hard layer has a thickness Hd such that 3<2 .pi.Hd/.lambda., where .lambda. denotes a wavelength of said acoustic wave element in the first-order mode.

A surface acoustic wave element comprising:

• a hard layer essentially consisting of diamond and a diamond-like carbon film;
• a piezoelectric layer formed directly on said hard layer;
• a silicon dioxide layer formed directly on said piezoelectric layer;
• and an electrode group sandwiched between said hard layer and said piezoelectric layer or between said piezoelectric layer and said silicon dioxide layer, for performing electro-mechanical conversion;
• wherein said piezoelectric layer essentially consists of ZnO and has a thickness Hz, and said silicon dioxide layer has a thickness Hs, such that the ratios 2 .pi.Hz/.lambda. and 2 .pi.Hs/.lambda., where .lambda. denotes a wavelength of said acoustic wave element in the first-order mode, are in a range wherein a propagation velocity v of said acoustic wave element is between about 8,000 m/s and about 10,000 m/s and a temperature coefficient .sigma. of said acoustic wave element is about 0.+-.10 ppm/.degree. C.