Etch stop region based fabrication of bonded semiconductor structures

A semiconductor structure, comprising:

• a bulk semiconductor substrate that comprises a planar surface and an opposing surface having a peripheral planar region surrounding a depression within a portion of the bulk semiconductor substrate, wherein a portion of the bulk semiconductor substrate between the planar surface and the peripheral planar region of the opposing surface is thicker than the portion of the bulk semiconductor substrate having the depression;
• a fabricated structure on the planar surface of the bulk semiconductor substrate, wherein the fabricated structure comprises a transistor having a gate, a source region, and a drain region, wherein the gate of the transistor is on the planar surface aligned with and opposite the depression to create a channel of the transistor in the portion of the bulk semiconductor substrate having the depression, and the source and drain regions of the transistor are in the portion of the bulk semiconductor substrate between the planar surface and the peripheral planar region of the opposing surface;
• a passivation layer on the opposing surface of the bulk semiconductor substrate including the peripheral planar region and the portion of the bulk semiconductor substrate having the depression aligned with the channel of the transistor and the gate;
• a handle substrate bonded to a surface of the fabricated structure;
• and
• electrical contacts extending through the source and drain regions in the peripheral planar region of the bulk semiconductor substrate, in which the passivation layer insulates the electrical contacts from directly contacting the source region and the drain region.