Embodiments of methods for forming contact structures and semiconductor devices thereof are disclosed. In an example, a semiconductor device includes an insulating layer, a conductive layer over the insulating layer, and a spacer structure in the conductive layer and in contact with the insulating layer. The semiconductor device also includes a first contact structure in the spacer structure and extending vertically through the insulating layer. The first contact structure includes a first contact portion and a second contact portion in contact with each other. An upper surface of the second contact portion is coplanar with an upper surface of the conductive layer.