Abstract: A conductively enclosed hybrid integrated circuit assembly for use with microwave and millimeter wave signals is disclosed. The enclosure utilizes a silicon substrate into which recesses are formed by conventional silicon etching processes to support individual MMIC chips with their surfaces flush with the unetched substrate surfaces. The assembly is covered with a thin solid dielectric layer, perforated over points of connection and followed by a metallization to provide point-to-point connections. The arrangement provides one or more levels of patterned metallizations with additional levels being provided either by additional dielectric layers or by forming the silicon substrate from three or more laminar elements and providing a patterned metallization on the surface of an intermediate element. Efficiency in signal grounding and in rf transmission line paths is assured by surface metallizations and the provision of low impedance paths through the substrate.