TRANSMISSION LINE AND ELECTRONIC DEVICE

A transmission line includes a first structure including a first insulating substrate and a ground conductor on the first insulating substrate, a second structure including a second insulating substrate and a signal line, ground conductors, and interlayer connection conductors on or in the second insulating substrate, a third insulating substrate including openings, and metal bonding materials that bond the structure and the structure to each other with the third insulating substrate interposed therebetween. The first and second insulating substrates are stacked with the third insulating substrate interposed therebetween to define hollow portions. The signal line and the ground conductor partially face each other across the hollow portions in a bonding direction. The ground conductor includes openings in regions that overlap the signal line but do not overlap the hollow portions when looking in plan view in the bonding direction.