Low capacitance interconnect structures and associated systems and methods

A semiconductor device, comprising:

• a semiconductor die having an opening, wherein the opening includes a sidewall extending at least partially through the substrate;
• and
• an interconnect structure, including—
• a conductor at least partially filling the opening, and
• a composite insulator at least between the sidewall and the conductor, wherein the composite insulator includes a first insulator on the sidewall, and a second insulator between the first insulator and the conductor, wherein the first insulator has a first thickness in the range between about 0.1 μm and 1.5 μm, and the second insulator has a second thickness in the range between about 0.01 μm to 1.5 μm.

A semiconductor device, comprising

• a semiconductor die having a hole extending into the die, wherein the hole has a base and a vertical sidewall extending toward the base;
• and
• a composite insulator in the hole and having a composite dielectric constant, the composite insulator including—
• a first insulator on the sidewall and having a first dielectric constant that is different the composite dielectric constant, and
• a second insulator on the first insulator and having a second dielectric constant that is different than the composite dielectric constant, and
• a conductor on the composite insulator.