We have demonstrated that Si single-electron or single-hole SOI-MOSFETs with the multi-dots channel have attractive new functions such as photon detection and single-electron transfer. Multi-dots formed by selective-oxidation-induced patterning of the thin SOI layer have been used in the experiments of photon detection, while, most recently, we have utilized smaller dots consisting of individual dopant potentials in single electron transfer devices. Furthermore, in order to directly observe spatial landscape of single charges in the channel region, we have developed Low Temperature-Kelvin Probe Force Microscopy and succeeded in detecting single-dopant potential in the channel region. In this paper, photon detection by these devices will be primarily described. © 2009 Materials Research Society.