<p>PURPOSE: A memory semiconductor device is provided to a single channel effect property by increasing the width of a transistor gate arranging on a base layer. CONSTITUTION: A memory semiconductor device comprises a first semiconductor layer(100) and a second semiconductor layer(200). The semiconductor layer is formed with a semiconductor wafer. The second semiconductor layer is formed with a semiconductor material layer. The first semiconductor layer and the second semiconductor layer are formed with the same semiconductor material. A first string structure(STR1) is formed on the semiconductor layer. A second string structure(STR2) is formed on the second semiconductor layer. The first string structure comprises a pair of first selecting transistors and a plurality of first memory transistors. The second string structure comprises a pair of second selection transistors and a plurality of second memory transistors.</p>
