US Patent 11705491 Etch profile control of gate contact opening

A method comprises forming a gate structure over a semiconductor substrate; etching back the gate structure; forming a gate dielectric cap over the etched back gate structure; depositing an etch-resistant layer over the gate dielectric cap; depositing a contact etch stop layer over the gate dielectric cap and an interlayer dielectric (ILD) layer over the contact etch stop layer; performing a first etching process to form a gate contact opening extending through the ILD layer and terminating prior to reaching the etch-resistant layer; performing a second etching process to deepen the gate contact opening, wherein the second etching process etches the etch-resistant layer at a slower etch rate than etching the contact etch stop layer; and forming a gate contact in the deepened gate contact opening.