Method for manufacturing semiconductor structure with mask structure

A method for forming a semiconductor structure, comprising:

• forming a dummy gate structure over a substrate;
• forming a spacer on a sidewall of the dummy gate structure;
• forming a resist layer covering a lower portion of the spacer and exposing an upper portion of the spacer;
• removing the upper portion of the spacer exposed by the resist layer, thereby only a lower sidewall of the dummy gate structure is covered by the spacer;
• removing the resist layer;
• forming a dielectric layer on an upper sidewall of the dummy gate structure;
• removing the dummy gate structure to form a trench;
• removing a portion of the dielectric layer to form a slope sidewall;
• forming a gate structure in a bottom portion of the trench;
• and
• forming a hard mask structure over the gate structure, wherein the hard mask structure covers the slope sidewall of the dielectric layer.

A method for forming a semiconductor structure, comprising:

• forming a dummy gate structure over a substrate;
• forming a sealing layer on a lower portion of a sidewall of the dummy gate structure;
• forming a dielectric layer on an upper portion of the sidewall of the dummy gate structure;
• removing the dummy gate structure to form a trench having a substantially straight sidewall formed of a sidewall of the sealing layer and a sidewall of the dielectric layer;
• etching the dielectric layer to form a slope sidewall, thereby forming a funnel shaped trench by the slope sidewall of the dielectric layer and the sidewall of the sealing layer;
• forming a gate structure in the funnel shaped trench;
• and
• forming a hard mask structure in the funnel shaped trench, wherein the hard mask structure is in direct contact with the sidewall of the sealing layer and the slope sidewall of the dielectric layer.