Methods for forming contact structures and semiconductor devices thereof

A semiconductor device, comprising:

• an insulating layer;
• a conductive layer over the insulating layer;
• a spacer structure in the conductive layer and in contact with the insulating layer;
• and
• a first contact structure in the spacer structure and extending vertically through the insulating layer,
• wherein the first contact structure comprises a first contact portion and a second contact portion in contact with each other, and
• a lower surface of the first contact portion is in contact with an upper surface of the second contact portion at a contact interface that is below an upper surface of the conductive layer.

A method for forming a semiconductor device, comprising:

• forming a spacer structure from a first surface of the base structure into the base structure;
• forming a first contact portion surrounded by the spacer structure;
• and
• forming a second contact portion in contact with the first contact portion, the second contact extending from a second surface of the base structure into the base structure.