Semiconductor device and manufacturing method thereof

A method for manufacturing a semiconductor device, comprising:

• forming a dummy gate structure including a dummy gate electrode layer having opposing side faces and side-wall insulating layers disposed on the opposing side faces of the dummy gate electrode layer;
• forming interlayer dielectric layers on the side-wall insulating layers;
• forming a mask pattern to cover a part of the dummy gate electrode layer, the side-wall insulating layers and the interlayer dielectric layer;
• removing a part of the dummy gate electrode layer not covered by the mask pattern, thereby forming a first space and a second space between the side-wall insulating layers and a pillar that is a remaining part of the dummy gate electrode layer;
• forming a first gate structure and a second gate structure in the first space and the second space, respectively;
• forming an opening by removing the pillar;
• and
• forming a separation plug by filling the opening with an insulating material.

A method for manufacturing a semiconductor device, comprising:

• forming a first fin structure and a second fin structure;
• forming an isolation insulating layer such that upper portions of the first and second fin structures protrude from the isolation insulating layer;
• forming, over the first and second fin structures, a first dummy electrode structure and a second dummy gate structure, each of which includes a dummy gate electrode layer having opposing side faces and side-wall insulating layers disposed on the opposing side faces of the dummy gate electrode layer;
• forming a mask pattern to cover a part of the first dummy gate electrode structure and the second dummy gate electrode structure;
• forming a first pillar and a second pillar by etching the dummy gate electrode layer of the first and second dummy gate structures respectively, using the mask pattern as an etching mask, so that a first space and a second space are formed between the side-wall insulating layers of the first dummy gate structure, a third space and a fourth space are formed between the side-wall insulating layers of the second dummy gate structure and the first pillar is formed between the first and second spaces and the second pillar is formed between the third space and the fourth space;
• forming a first gate structure and a second gate structure in the first space and the second space, respectively, and a third gate structure and a fourth gate structure in the third space and the fourth space, respectively;
• removing the first and second pillars so that a first opening and a second opening are formed;
• and
• forming a first separation plug and a second separation plug by filling the first and second openings with an insulating material.