| 摘要 |
PURPOSE:To realize low energy data writing through in implantation and twice or more capacity in the same chip size, by adopting an inverse multigate TFT structure wherein the surfaces of gate electrodes are almost uniformly arranged, in a large capacity mask ROM. CONSTITUTION:On the main surface of a P-type silicon substrate 1, first gate electrodes 2 and second gate electrodes 4 are so formed via an isolation oxide film 3 that the respective surfaces become almost uniform. A gate oxide film 5 and a silicon film 6 are formed so as to cover the electrodes. By forming source drain electrodes 7a, 7b, an inverse multigate TFTMOSFET can be formed. Phosphorus or the like is ion-implanted only in transistors for which data writing is wanted. Since the silicon film 6 is thin, low acceleration energy may be used, and the implantation precision is improved. Further the surfaces of the gate electrodes are uniformly arranged, so that channel offset can be evaded. |
