High frequency apparatus for transmitting or processing high frequency signal

A high frequency apparatus comprising:

• a first substrate having a recessed portion in a surface of said first substrate;
• a first grounding conductor on said first substrate and at least partially in the recessed portion of said first substrate;
• a dielectric support film supported on the surface of said first substrate, a part of said dielectric support film being disposed opposite the recessed portion of said first substrate, with an air space between said first substrate and the part of said dielectric support film, wherein said dielectric support film includes at least one opening portion passing through said dielectric support film opposite the air space and used in forming the air space;
• an interconnecting conductor for transmission and on a part of a surface of said dielectric support film;
• and
• second grounding conductors on the surface of said dielectric support film, located on opposite sides of said interconnecting conductor film for transmission, with spacing between said interconnecting conductor and each of said second grounding conductors.