Abstract: A tunable microwave resonator, including walls delimiting a cavity, the walls including a first wall formed with an opening; a tuning screw extending in the opening, a cylindrical dielectric resonator disposed in the cavity, and a dielectric support projecting in the opening, the dielectric support acting as a spacer and rigidly connecting the dielectric resonator to the tuning screw. The cavity and the dielectric resonator are excitable in one or more resonant modes of an electromagnetic field, wherein a current induced by the resonant modes is transferred outside the cavity; and a toroidal extension formed on the first wall inside the cavity and surrounding the opening, the toroidal extension extending a given length inside the cavity, the toroidal extension reducing a thermal effect on the resonance frequency, and increasing mechanical stability.