In some embodiments of the present disclosure, a method for forming a fin-type field effect transistor is described. A substrate embedded with a stop layer is provided. The substrate is patterned to form trenches in the substrate and fins between the trenches. Insulators are formed in the trenches of the substrate. A stack structure is formed over the substrate and on the insulators, and the stack structure covers portions of the fins. Recesses are formed in the fins by using the stop layer in the fins as an etching stop layer to remove portions of the fins that are not covered by the stack structure. Strained material portions are formed in the recesses between the insulators and on two opposite sides of the stack structure. After removing the stack structure, a gate stack is formed over the substrate and on the insulators. The strained material portions are located on two opposite sides of the gate stack.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.