There are several transmission line geometries that can be used in constructing a DTL.
The simplest geometry is a pair of flat conductors separated by a dielectric. A voltage source is connected to one end and the load is connected to the other.
A second approach is to form the DTL as a coaxial cable. As an example, small round conductor can be coated with a dielectric. A second conductor is then plated over the dielectric. Several of these coaxial filaments could be routed in parallel forming a DTL. Using this technique, the characteristic impedance in theory could be milliohms.
Another approach is to build the DTL transmission line as two closely spaced traces. The traces could be folded in the form of a maze or carried over some distance. A maze configuration could also be a part of a die.