A semiconductor device is provided including a substrate including a trench. A first conductive pattern is disposed within the trench. The first conductive pattern has a width smaller than a width of the trench. A first spacer extends along at least a portion of a side surface of the first conductive pattern and the trench. A second spacer at least partially fills the trench adjacent to the first spacer. An air spacer is provided including a first portion between the first spacer and the second spacer, and a second portion disposed on the second spacer and the first portion. A width of the second portion of the air spacer is greater than a width of the first portion of the air spacer.