A device (11, 40) comprising an evanescent-mode electromagnetic-wave cavity resonator (1900, 2100) comprising: a lower cavity portion (1902, 2102) including: a first cavity surface defining a first cavity (106, 1906a, 2106a), a first mating surface around the periphery of the first cavity defining a first plane, and a conductive layer over the first cavity surface; an upper cavity portion (1904, 2104) including: a second cavity surface defining a second cavity (1906b, 2106b), a second mating surface around the periphery of the second cavity defining a second plane, the first cavity (1906a, 2106a) and the second cavity (1906b, 2106b) defining a volume, and a conductive layer over the second cavity surface; and an in-plane resonator structure (1903, 2103) including: a conductive tuning structure (1910, 2110) comprising a post extending transversely within the volume between the first plane and the second plane culminating at a distal end of the post in an integrally formed post top, wherein the post top has a width larger than a width of the post; and a support ring structure (1911, 2103) extending between the first plane and the second plane, a first surface of the support ring structure being connected with the first mating surface and a second surface of the support ring structure being connected with the second mating surface to physically support the tuning structure (1910, 2110); a distal surface (1922, 2122) of the post top of the tuning structure (1910, 2110) being separated from the closest surface thereto of the support ring structure (1911, 2103) by a gap distance in a region between the first plane and the second plane, a resonant frequency of at least one evanescent electromagnetic wave mode of the resonator (1900, 2100) being defined at least partially by the gap distance; wherein said closest surface is a portion of an inner surface of the support ring structure adjacent to the post top. a lower cavity portion (1902, 2102) including: a first cavity surface defining a first cavity (106, 1906a, 2106a), a first mating surface around the periphery of the first cavity defining a first plane, and a conductive layer over the first cavity surface; a first cavity surface defining a first cavity (106, 1906a, 2106a), a first mating surface around the periphery of the first cavity defining a first plane, and a conductive layer over the first cavity surface; an upper cavity portion (1904, 2104) including: a second cavity surface defining a second cavity (1906b, 2106b), a second mating surface around the periphery of the second cavity defining a second plane, the first cavity (1906a, 2106a) and the second cavity (1906b, 2106b) defining a volume, and a conductive layer over the second cavity surface; and a second cavity surface defining a second cavity (1906b, 2106b), a second mating surface around the periphery of the second cavity defining a second plane, the first cavity (1906a, 2106a) and the second cavity (1906b, 2106b) defining a volume, and a conductive layer over the second cavity surface; and an in-plane resonator structure (1903, 2103) including: a conductive tuning structure (1910, 2110) comprising a post extending transversely within the volume between the first plane and the second plane culminating at a distal end of the post in an integrally formed post top, wherein the post top has a width larger than a width of the post; and a support ring structure (1911, 2103) extending between the first plane and the second plane, a first surface of the support ring structure being connected with the first mating surface and a second surface of the support ring structure being connected with the second mating surface to physically support the tuning structure (1910, 2110); a distal surface (1922, 2122) of the post top of the tuning structure (1910, 2110) being separated from the closest surface thereto of the support ring structure (1911, 2103) by a gap distance in a region between the first plane and the second plane, a resonant frequency of at least one evanescent electromagnetic wave mode of the resonator (1900, 2100) being defined at least partially by the gap distance; wherein said closest surface is a portion of an inner surface of the support ring structure adjacent to the post top. a conductive tuning structure (1910, 2110) comprising a post extending transversely within the volume between the first plane and the second plane culminating at a distal end of the post in an integrally formed post top, wherein the post top has a width larger than a width of the post; and a support ring structure (1911, 2103) extending between the first plane and the second plane, a first surface of the support ring structure being connected with the first mating surface and a second surface of the support ring structure being connected with the second mating surface to physically support the tuning structure (1910, 2110); a distal surface (1922, 2122) of the post top of the tuning structure (1910, 2110) being separated from the closest surface thereto of the support ring structure (1911, 2103) by a gap distance in a region between the first plane and the second plane, a resonant frequency of at least one evanescent electromagnetic wave mode of the resonator (1900, 2100) being defined at least partially by the gap distance; wherein said closest surface is a portion of an inner surface of the support ring structure adjacent to the post top.