Dielectric cap structure in semiconductor devices and methods of manufacturing the same

A semiconductor device, comprising:

• a channel structure;
• a first gate structure straddling the channel structure;
• a source/drain structure, adjacent the first gate structure, that is coupled to an end of the channel structure;
• a first contact structure disposed over and in contact with the source/drain structure;
• a gate spacer disposed between the first gate structure and the first contact structure;
• a nitride-based conformal layer extending over the first contact structure, the gate spacer, and at least a portion of the first gate structure;
• an oxide-based layer disposed over the nitride-based conformal layer;
• and
• a second contact structure that penetrates through a first portion of the oxide-based layer and the nitride-based conformal layer to be in contact with the first gate structure, wherein the first portion of the oxide-based layer extends to below a top surface the nitride-based conformal layer.

A method for making semiconductor devices, comprising:

• forming a semiconductor device that at least includes a gate structure straddling a channel structure and a first epitaxial structure adjacent the gate structure, wherein the first epitaxial structure is overlaid by an interlayer dielectric;
• forming a nitride-based conformal layer that extends over the gate structure and the interlayer dielectric;
• forming an oxide-based layer over the nitride-based conformal layer, wherein the oxide-based layer includes a first portion that fills up a recess above the gate structure;
• and
• forming a first contact structure that extends through the first portion of the oxide-based layer and the nitride-based conformal layer to couple to the gate structure.