Flash memory devices include a pair of elongated, closely spaced-apart main active regions in a substrate. A sub active region is also provided in the substrate, extending between the pair of elongated, closely spaced-apart main active regions. A bit line contact plug is provided on, and electrically contacting, the sub active region and being at least as wide as the sub active region. An elongated bit line is provided on, and electrically contacting, the bit line contact plug remote from the sub active region.