| With the development of wireless communication technology, the communication systems are becoming smaller and smaller. Meanwhile wide band communications are in great demand which make the frequency of communication becoming much higher. In order to meet the development of communication devices, materials with excellent RF properties are under intense research. In this context, BaxSr1-xTiO3 (BST) ferroelectric film materials are attracting more and more attention.At paraelectric phase, BST ferroelectric material shows high dielectric constant with good stability and its'dielectric constant varies with the DC bias. The Curie-Temperature of Ba0.5Sr0.5TiO3 is -5℃and works at paraelectric phase. These factors make Ba0.5Sr0.5TiO3 a good candidate in the applications of phase shifters, filters, and varistor. In this paper, we prepared (100)-oriented LaNiO3 films with RF magnetron-controlled sputtering method, and then Ba0.5Sr0.5TiO3 was deposited (100)-oriented with LaNiO3 (LNO) as buffer layer. Through XRD, AFM, SEM and CV test, it has been shown that LNO buffer layer not only enhanced BST (100) orientation but also improved the tunability from 35% to 45%, and decreased the less tangent from 0.2 to 0.05. Then the effect of BST thickness and LNO thickness on the capacitance was investigated and the mechanism was also analyzed.Based on MEMS micro-fabrication method and the good properties of the materials, a parallel plate film capacitor was fabricated and low frequency (1MHz) property was tested. CPW (coplanar wave-guide) structure was fabricated and high frequency (0-20GHz) was conducted.
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