To provide a variable capacitor having a wide capacitance range against a narrow voltage range.

A variable voltage capacitor 10 manufactured on a semiconductor substrate 11 incorporates a gate structure 62 and a well 22 underlying the structure 62. A buried layer 15 doped at a high concentration and a contact area 31 doped at a high concentration in the substrate 11 form a low-resistance conducting path from the well 22 to the surface 17 of the substrate 11. The variable voltage capacitor 10 is constructed by using a multi-finger layout. When the voltage applied across the capacitor 10 changes during operation, the width of a depletion area in the well 22 changes and, accordingly, the capacitance of the capacitor 10 also changes.