Solid-state quantum dots, in which the charge and spin of excess carriers are controllable, are strong candidates for future nanoelectronics and quantum information processing. Devices based on SiGe are compatible with conventional silicon complementary metal-oxide-semiconductor processing, which allows for large-scale integration. The fabrication of SiGe double quantum dots using electron beam lithography and reactive ion etching is described. Devices are characterized electrically at cryogenic temperatures and the mixing of two microwave signals is demonstrated. (C) 2003 American Vacuum Society.