A method for enabling fabrication of memory devices requiring no or minimal additional mask for fabrication having a low cost, a small footprint, and multiple-time programming capability is disclosed. Embodiments include: forming a gate stack on a substrate; forming a source extension region in the substrate on one side of the gate stack, wherein no drain extension region is formed on the other side of the gate stack; forming a tunnel oxide liner on side surfaces of the gate stack and on the substrate on each side of the gate stack; forming a charge-trapping spacer on each tunnel oxide liner; and forming a source in the substrate on the one side of the gate stack and a drain in the substrate on the other side of the gate stack.