Integrated circuit devices including metal structures having a curved interface and methods of forming the same

A method of forming an integrated circuit device, the method comprising:

• providing an underlying structure including a substrate and a first insulating layer;
• forming a first metal structure, a first adhesion pattern, and a second insulating layer on the first insulating layer, wherein the second insulating layer is on a side surface of the first metal structure, the first metal structure has a width decreasing as a distance from the first insulating layer increases, and the first metal structure comprises a metal pattern, a second adhesion pattern that is between the first insulating layer and the metal pattern, such that the first adhesion pattern contacts both a side surface of the metal pattern and a side surface of the second adhesion pattern;
• and
• forming a second metal structure on the first metal structure,
• wherein the metal pattern of the first metal structure comprises a contact portion that protrudes upwardly beyond an upper surface of the second insulating layer and contacts the second metal structure.