Methods of fabricating a semiconductor integrated circuit having thin film transistors using an SEG technique are provided. The methods include forming an inter-layer insulating layer on a single-crystalline semiconductor substrate. A single-crystalline semiconductor plug extends through the inter-layer insulating layer, and a single-crystalline epitaxial semiconductor pattern is in contact with the single-crystalline semiconductor plug on the inter-layer insulating layer. The single-crystalline epitaxial semiconductor pattern is at least partially planarized to form a semiconductor body layer on the inter-layer insulating layer, and the semiconductor body layer is patterned to form a semiconductor body. As a result, the semiconductor body includes at least a portion of the single-crystalline epitaxial semiconductor pattern. Thus, the semiconductor body has an excellent single-crystalline structure. Semiconductor integrated circuits fabricated using the methods are also provided.