The present invention relates to the formation of a vacuum electronics circuit by the fusion bonding of multiple substrate wafers, e.g., silicon, copper, or other suitable conductive material, each etched using DRIE, cut using EDM, or machined by other suitable means. Other aspects of the invention relate to the alignment of a cathode with tube by fusion bonding the cathode wafer to a tube built using the fabrication methods described herein. Yet other aspects involve the alignment of dies or wafers during the fabrication of a vacuum electronics device using the “lego” technique outlined herein. In yet other aspects, fabrication methods are described.