Abstract: An RF circuit module comprising a first RF semiconductor device 19 mounted within a cavity 4 surrounded by a wall 3 of a first dielectric circuit board 1, and a second RF semiconductor device 29 mounted to a second dielectric circuit board 2 placed on the wall 3. A metal base 11 is disposed on the first circuit board 1 and a number of embedded conductors 13 such as via holes are embedded within the wall 3 and arranged to surround the cavity 4 so that each having one end electrically connected to the metal base 11 and the other end exposed and arranged to surround the cavity 4. A metal cover 12 is sealingly attached to the first circuit board 1 to cover the second circuit board 2 and the second RF semiconductor device 29 and electrically connected at the upper surface of the wall 3. Therefore, the first and second RF semiconductor devices are electrically shielded and hermetically sealed, providing an RF circuit module of small-sized and high-performance.