There are various methods for producing device-worthy Silicon-on-Insulator
films, most, however, are unsuitable for fabrication of 3D integrated
structures. The laser recrystallization technique is currently the only one
which has produced single-crystal devices for 3D ICs. Improvements on this
technique have been such that defects such as grain boundaries can be
localized and even eliminated. High speed CMOS circuits with VLSI features
have been realized as well as new devices which take advantage of the 3D
arrangement of vertically integrated structures. Although 3D integration is
still in the early stages of development, it has already opened up new
perspectives for applications such as high speed circuits, dense memories,
and sensors.