PURPOSE: To easily form a piezo-electric film and, at the same time, improve the characteristic at high frequencies of the titled device, by forming the substrate by installing an aluminum nitride single crystal epitaxial layer on a silicon single crystal layer composed of (110) crystal planes.
CONSTITUTION: A silicon single crystal substrate 1 is composed of a silicon crystal cut along (110) crystal planes or equivalent planes. An aluminum nitride (AlN) single crystal layer 2 is formed on the silicon single crystal substrate 1 in such a way that the piezo-electric axis will become perpendicular to the plane of the substrate 1. Then, a comb-shaped elastic surface wave driving electrode 3 and detecting electrode 4 are formed on the layer 2. The phase speed Vp of the elastic surface wave against the film pressure (h) of the layer 2 rises upward to the right from about 4,482m/sec. to about 4,680m/sec. within a range of 0.0∼ 1.9 of 2πh/λ (λ is the wave length of the elastic surface wave). When the 2πh/λ is about 1.9, the mode as the elastic surface wave disappears and a bulk wave appears.
TSUBOUCHI KAZUO
SUKAI KAZUYOSHI
TSUBOCHI KAZUO
| JPS5778206A | 1982-05-15 |