Electrically tunable device and a method relating thereto
The present invention relates to a thin film ferroelectric varactor device (10) comprising a substrate layer (1), a ferroelectric layer structure (12) and an electrode structure (91,92). The ferroelectric layer structure (12) comprises a number of ferroelectric layers (2,4) and a number of intermediate buffer layers (3) arranged in an alternating manner. At least a first (2) and a second (4) layer of said ferroelectric layers have different Curie temperatures, i.e. the dielectric constant of the first ferroelectric layer (12) has a maximum at a temperature which is different from the temperature at which the dielectric constant of the second ferroelectric layer (4) has a maximum.