| 摘要 |
PROBLEM TO BE SOLVED: To enhance the degree of integration of a mask ROM. SOLUTION: Transistor cells comprised in a mask ROM comprises a common source line 30 formed on the base of a groove 16, word lines 20A consisting of gate electrodes formed on the side walls of the groove 16, and drain regions 22 formed on the upside of a protrusion sandwiched between the grooves 16. The drain regions 22 are separated from each other in the direction of the groove 16, and the source line 30 is made to extend in the direction of the groove 16 due to the structure of the groove 16 deeper than an element isolation region 12. The mask ROM is programmed depending on whether it is connected to a bit line 36 through the intermediary of a contact hole 38 or not. The mask ROM can be also programmed by adjustment of the transistor cells in Vt H. A gate electrode is formed on the side wall of a groove, whereby a channel can be set vertical to the surface of a substrate, and the mask ROM can be enhanced in degree of integration. Gate lines 20A located on both the sides of a protrusion can be connected together in parallel, so that the transistor cells can be enhanced twice as much in driving capacity. |
