Method for fabricating a strained structure

A method for fabricating a semiconductor device, comprising:

• providing a substrate including an isolation structure;
• forming a recess cavity comprising an upper portion and a lower portion in the substrate, wherein one sidewall of the recess cavity is dielectric and other sidewall of the recess cavity is the substrate;
• forming a dielectric film on the substrate sidewall portion, a bottom portion of the recess cavity, and a sidewall of the isolation structure;
• removing the dielectric film on the bottom portion of the recess cavity;
• epi-growing a first strained layer in the lower portion of the recess cavity adjacent to a first portion of the dielectric film on the substrate sidewall portion and adjacent to a second portion of the dielectric film on the sidewall of the isolation structure, the first strained layer being between the first portion of the dielectric film on the substrate sidewall portion and the second portion of the dielectric film on the sidewall of the isolation structure;
• removing a portion of the dielectric film not adjacent to the first strained layer;
• and
• epi-growing a second strained layer in the upper portion of the recess cavity.