Fin field effect transistor and method for fabricating the same

A fin field effect transistor (FinFET), comprising:

• a substrate having a semiconductor fin, wherein the semiconductor fin comprises a first portion and a plurality of second portions, the first portion is disposed between the second portions;
• a gate dielectric layer on a top surface and upper sidewalls of the first portion of the semiconductor fin;
• a gate electrode on the gate dielectric layer;
• a plurality of blocking layers on lower sidewalls of the first portion of the semiconductor fin, on sidewalls of the second portions of the semiconductor fin, and on a top surface of the substrate;
• a plurality of strained layers over the second portions of the semiconductor fin;
• and
• a plurality of isolation structures on the blocking layers, wherein a material of the blocking layers is different from a material of the isolation structures.

A method for fabricating a fin field effect transistor (FinFET), comprising:

• providing a substrate;
• removing a portion of the substrate to form a plurality of trenches in the substrate and semiconductor fins between the trenches;
• forming a plurality of blocking material layers at sidewalls of the semiconductor fins and on bottom surfaces of the trenches;
• forming an isolation material over the substrate to cover the blocking material layers and fill in the trenches, wherein a material of the blocking material layers is different from a material of the isolation material;
• partially removing the isolation material and the blocking material layers to form a plurality of isolation structures and a plurality of blocking layers, wherein the semiconductor fins protrude from the isolation structures;
• and
• forming a gate stack across the semiconductor fins, the blocking layers and the isolation structures.