| 摘要 |
PURPOSE:To make it possible to store and hold an optical signal as an electric signal by combination of a photodiode and a semiconductor storage device which is a combination of a volatile semiconductor memory and a nonvolatile semiconductor memory. CONSTITUTION:A MOS transistor MT2 constitutes an EEPROM as a nonvolatile semiconductor memory with a floating gate 6 established below a usual control gate G2. A MOS transistor MT3 is a mode switching one to switch the nonvolatile semiconductor memory to make it work as an EEPROM or a volatile semiconductor memory DRAM. Voltage is applied from a terminal 7 to the gate G3 and the gate G2 of the MOS transistor MT2. Between a diffusion layer (N layer) 4 and a P-type Si substrate 8, a P-N junction photodiode PD is formed. With an optical signal applied to the photodiode PD to be converted into an electric signal, the data on the signal are sent to the EEPROM to be stored. By this method, the data can be stored and held without being backed up by a battery. |
