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 first non-single-crystal layer is arranged beneath the trench isolation regions and the active device region. A second non-single-crystal layer is arranged beneath the trench isolation regions and the active device region. The first non-single-crystal layer is arranged between the second non-single-crystal layer and the active device region.