There is disclosed a variable capacitance circuit which comprises: first to
Nth variable capacitance elements C1-CN (N is an odd number) sequentially
connected in series between an input terminal I and an output terminal O, whose
capacitances change depending on voltage applied thereto; an ith bias line on the
input terminal side provided between an input terminal portion of the first variable
capacitance element and a connection point between a 2ith variable capacitance
element and a (2i+1)th variable capacitance element; and an ith bias line on the
output terminal side provided between an output terminal portion of the Nth variable
capacitance element and a connection point between a (2i-1)th variable capacitance
element and the 2ith variable capacitance element, where N and i are integers satisfying
N=2n+1, n1, 1in. With the arrangement of the variable capacitance
circuit, it is possible to provide a variable capacitance thin film capacitor device
whose capacitance change ratio is small in a radio frequency region and large in
a direct current region can be provided. Furthermore, a radio frequency device
utilizing the variable capacitance thin film capacitor device can be provided.