Method for forming semiconductor-on-insulator (SOI) substrate and recycle substrate

A method for forming a semiconductor substrate, comprising:

• receiving a first substrate comprising a first layer, a second layer and a third layer between the first layer and the second layer;
• etching the first layer, the second layer and the third layer to form a plurality of mesas separated from each of by a plurality of trenches, wherein in each of the plurality of mesas, a width of the third layer is less than a width of the first layer and less than a width of the second layer, and each of the first layer, the second layer and the third layer is exposed through sidewalls of the trenches;
• and
• sealing the plurality of trenches with an epitaxial semiconductor material to form a plurality of first voids, wherein the first voids and the mesas are alternately arranged, wherein bottoms of the plurality of first voids are higher than a bottom surface of the first layer.

A method for forming a recycle substrate, comprising:

• forming a multilayered structure over a surface of a first substrate, wherein the multilayered structure comprises a first semiconductor layer, a second semiconductor layer and a plurality of semiconductor islands between the first semiconductor layer and the second semiconductor layer, wherein the semiconductor islands comprise a material different from a material of the first semiconductor layer and different from a material of the second semiconductor layer;
• forming a device layer over the multilayered structure, wherein the device layer is separated from the multilayered structure;
• bonding the device layer to a second substrate;
• separating the device layer and the second substrate from the first substrate along the plurality of semiconductor islands, wherein the plurality of semiconductor islands are divided into a first portion coupled to the first semiconductor layer and a second portion coupled to the second semiconductor layer;
• and
• removing the first portions and the first semiconductor layer from the first substrate to expose the surface of the first substrate.