Radiofrequency filter

A radiofrequency (RF) filter, comprising:

• a substrate;
• an isolation structure disposed in the substrate;
• an electrically conductive structure disposed on the isolation structure;
• a spacer structure disposed on the substrate and located on a sidewall of the electrically conductive structure;
• a dielectric layer disposed on the electrically conductive structure;
• a patterned electrically conductive film disposed on the dielectric layer, wherein at least a part of the dielectric layer is located between the electrically conductive structure and the patterned electrically conductive film in a vertical direction;
• and
• a first contact structure and a second contact structure, wherein the first contact structure and the second contact structure are disposed on and electrically connected with the patterned electrically conductive film, at least a part of the dielectric layer is sandwiched between the patterned electrically conductive film and the electrically conductive structure in the vertical direction, and the dielectric layer is directly connected with the patterned electrically conductive film and the electrically conductive structure,
• wherein the patterned electrically conductive film, the electrically conductive structure, and the dielectric layer sandwiched between the patterned electrically conductive film and the electrically conductive structure in the vertical direction constitute a capacitor structure.