Resonator, filter, and communication device

A resonator, comprising:

• a shield housing comprising a first conductor portion located on a first direction side, and a second conductor portion located on a second direction side which is opposite to the first direction side, the shield housing having a cavity therein;
• a first resonant element which is shaped in a column and lies within the cavity, the first resonant element comprising a first direction end joined to the first conductor portion, and a second direction end spaced from the shield housing;
• a second resonant element which is constituted by a tubular dielectric and lies within the cavity, the second resonant element comprising a second direction end joined to the second conductor portion and a first direction end spaced from the shield housing, and surrounding the first resonant element at a distance from the first resonant element;
• and
• an inner wall-covering layer formed of a conductor, the inner wall-covering layer being located on an inner wall surface of the second resonant element.