Abstract: An hermetic sealed microwave diode package having high thermal conductivity and very low parasitic impedances. The diode chip is mounted upon a diamond member embedded in a copper base member so that the diamond mounting surface and the copper base member surface are coplanar. A fused silica insulator ring produced by selective grit blasting surrounds the chip and is mounted likewise entirely on the diamond surface. The silica insulator has a height comparable to the thickness of the semiconductor chip and the enclosure is completed by a metal covering member which includes a contact to the top surface of the diode chip. The package thereby has extremely short conductive paths and low capacitance by virtue of the very small silica insulator ring.