Methods of ion implantation combined with annealing using a pulsed laser or a furnace for cutting substrate in forming semiconductor devices and semiconductor devices including the same are disclosed. In an embodiment, a method includes forming a transistor structure of a device on a first semiconductor substrate; forming a front-side interconnect structure over a front side of the transistor structure; bonding a carrier substrate to the front-side interconnect structure; implanting ions into the first semiconductor substrate to form an implantation region of the first semiconductor substrate; and removing the first semiconductor substrate. Removing the first semiconductor substrate includes applying an annealing process to separate the implantation region from a remainder region of the first semiconductor substrate. The method also includes forming a back-side interconnect structure over a back side of the transistor structure.