Electronic systems with through-substrate interconnects and mems device

Disclosed is a method of forming an interconnect in a substrate having a first surface and a second surface. The method includes forming an insulating structure abutting the first surface and defining a closed loop around a via in the substrate and forming an insulating region abutting the second surface such that the insulating region contacts the insulating structure and separates the via from a bulk region of the substrate. Forming the insulating structure includes etching the substrate beginning from the first surface to form a trench, filling the trench to form a seam portion, and converting a first portion of the substrate to a first solid portion to form the closed loop.