A method for fabricating a semiconductor device includes forming a plurality of layers which are stacked as a bottom layer, an MTJ layer, and a top layer, patterning the top layer and the MTJ layer using an etch mask pattern to form a top layer pattern and an MTJ pattern, forming a carbon spacer on the sidewalls of the MTJ pattern and the top layer pattern to protect the MTJ pattern and the top layer pattern, and patterning the bottom layer using the carbon spacer and the etch mask pattern as an etch mask to form a bottom layer pattern.