US Patent 10192779 Bulk substrates with a self-aligned buried polycrystalline layer

Structures with altered crystallinity beneath semiconductor devices and methods associated with forming such structures. Trench isolation regions surround an active device region composed of a single-crystal semiconductor material. A non-single-crystal layer has a first section arranged beneath the trench isolation regions and a second section arranged beneath the active device region. The first section of the non-single-crystal layer has a first width in a vertical direction. The second section of the non-single-crystal layer has a second width in the vertical direction that is less than the first width of the first section of the non-single-crystal layer.