Etch profile control of gate contact opening

A method comprising:

• forming a first gate dielectric cap over a first gate structure and a second gate dielectric cap over a second gate structure;
• depositing an etch-resistant layer over the first gate dielectric cap and the second gate dielectric cap;
• depositing a contact etch stop layer over etch-resistant layer, and an interlayer dielectric (ILD) layer over the contact etch stop layer;
• performing a first etching process to form a first gate contact opening and a second gate contact opening extending through the ILD layer, wherein the first gate contact opening has a smaller width than the second gate contact opening;
• performing a second etching process to extend the first and second gate contact openings toward the first and second gate structures, wherein after the second etching process etches through the etch-resistant layer, a sidewall profile of the first gate contact opening becomes more vertical than before etching the etch-resistant layer;
• and
• after performing the second etching process, forming a first gate contact in the first gate contact opening and a second gate contact in the second gate contact opening.

A device comprising:

• source/drain epitaxial structures over a substrate;
• source/drain contacts over the source/drain epitaxial structures, respectively;
• a gate structure laterally between the source/drain contacts;
• a gate dielectric cap over the gate structure and having a bottom surface below top surfaces of the source/drain contacts;
• an oxide-based etch-resistant layer over the gate dielectric cap;
• a nitride-based etch stop layer over the oxide-based etch-resistant layer;
• an interlayer dielectric (ILD) layer over the nitride-based etch stop layer;
• and
• a gate contact extending through the ILD layer, the nitride-based etch stop layer, the oxide-based etch-resistant layer, and the gate dielectric cap to electrically connect with the gate structure.