A method for forming an SOI substrate is provided. The method includes following operations. A recycle substrate is received. A first multilayered structure is formed on the recycle substrate. A trench is formed in the first multilayered structure. A lateral etching is performed to remove portions of sidewalls of the trench to form a recess in the first multilayered structure. The trench and the recess are sealed with an epitaxial layer, and a potential cracking interface is formed in the first multilayered structure. A second multilayered structure is formed over the first multilayered structure. The device layer of the recycle substrate is bonded to an insulator layer over an carrier substrate. The first multilayered structure is cleaved along the potential cracking interface to separate the recycle substrate from the second multilayered structure, the insulator layer and the carrier substrate. The device layer is exposed.