Semiconductor device and method for fabricating the same

A method for fabricating semiconductor device, comprising:

• forming a gate structure on a substrate;
• forming a first spacer adjacent to and directly contacting the gate structure, wherein the first spacer comprises silicon carbon nitride (SiCN) and a L-shape;
• forming a second spacer adjacent to and directly contacting the first spacer, wherein the second spacer comprises silicon oxycarbonitride (SiOCN) and an I-shape;
• forming a third spacer adjacent to and directly contacting the first spacer and the second spacer, wherein the third spacer comprises SiN and an I-shape;
• and
• forming a source/drain region adjacent to two sides of the second spacer.