A semiconductor device includes an insulating layer on a semiconductor substrate, a bit line including TiAl and disposed on the insulating layer, a sidewall layer disposed on opposite sides of the bit line, a word line including TiN and disposed on the sidewall layer intersecting the bit line, and an air gap in an intersection region of the bit line and the word line. The thickness of the sidewall layer is larger than the thickness of the bit line. By having the TiAl bit line and TiN word line, the uniformity of the bit line and word line can be easily controlled to improve the performance of the semiconductor device.