The present application discloses a method for fabricating a semiconductor device. The method includes: providing a substrate including a plurality of first regions and second regions; forming a plurality of bit line contacts over the first regions of the substrate; forming a plurality of bit lines respectively over the plurality of bit line contacts; forming a plurality of capacitor contacts respectively over the second regions of the substrate; forming a plurality of capacitor plugs respectively over the plurality of capacitor contacts; forming a plurality of first spacers respectively over a plurality of protruding portions of the plurality of capacitor plugs, wherein a width of the first spacer is larger than a width of the capacitor plug; and forming a plurality of capacitor structures over the plurality of first spacers; wherein at least one of the plurality of bit lines is an undulating stripe extending between two adjacent capacitor contacts.