Resonant element, filter, and diplexer

A resonant element in which a plurality of electrodes are provided inside a dielectric, the resonant element comprising:

• at least one first plane electrode;
• a second plane electrode facing the at least one first plane electrode in a normal direction of the at least one first plane electrode;
• a first via electrode connecting the at least one first plane electrode and the second plane electrode to define a first inductor;
• a third plane electrode defining a first capacitor together with the second plane electrode;
• a second inductor connecting the at least one first plane electrode and the third plane electrode;
• and
• a third inductor connecting the at least one first plane electrode and the third plane electrode;
• wherein
• the second inductor includes at least one second via electrode connecting the at least one first plane electrode and the third plane electrode;
• the third inductor includes at least one third via electrode connecting the at least one first plane electrode and the third plane electrode;
• and
• each of the at least one second via electrode and the at least one third via electrode is a columnar conductor extending in an extending direction of the first via electrode.