| 摘要 |
PURPOSE:To improve the dielectric strength by forming a piezoelectric film on an insulating substrate on the surface of which plural pairs of positive and negative comb line electrodes are formed, forming the film made of a dielectric substance on the piezoelectric film and further forming a conductive film on the dielectric film so as to spread the interval between the comb line electrode and the conductive film. CONSTITUTION:The film 6 made of the dielectric substance such as SiO2 is formed between the piezoelectric film 4 and the conductive films 5, 5'. SiO2 is used mainly for the film 6 made of the dielectric substance and since the SiO2 is a chemically very stable substance, the film is not susceptible to the adverse effect of environmental conditions, the electrostatic dielectric strength level is improved and also stable quality is ensured. Then the electrostatic dielectric strength level is improved more than twice the initial value by forming the film thickness of the SiO2 as >=1mu, and the surface wave filter suitable for a VIF circuit or the like of a television receiver and a video tape recorder is obtained. |
