The decrease in nucleation rate for solid-phase crystallization was investigated. SiO2 underlayers were treated with various wet chemicals before depositing amorphous Si (a-Si) films in a low pressure chemical vapor deposition tube, using disilane (Si2H6) at 480 degrees C. These amorphous Si films were crystallized by subsequent annealing at 600 degrees C for various times. The nucleation rate depended on the SiO2 surface treatment by HF:H2O (DHF) or NH4OH:H2O2:H2O (APM). Consequently poly-Si films with a large grain size, two or three times as large as that without any treatment could be obtained. The steady-state nucleation rate decreased as the degree of hydrophilicity of the SiO2 underlayer was enhanced, whereas the incubation time for the nucleation remained almost constant for the degree of hydrophilicity. Moreover, attenuated total reflection measurements indicated that the amount of the OH groups on the SiO2 surface was increased by the DHF treatment. These results indicate that nucleation occurred at the a-Si/SiO2 interface and that this depended on the amount of OH groups on the SiO2 surface at room temperature.