Correlation between microstructure parameter of a-Si:H films and cluster amount in silane discharges is revealed by using a cluster-suppressed plasma CVD method. The microstructure parameter R-alpha of a-Si:H films decreases below 0.003 with decreasing the cluster amount. A Schottky solar cell of a-Si:H films of Ralpha = 0.057 shows a high initial fill factor (FF) of 0.57 and high stabilized FF of 0.53. In addition, amount of clusters incorporated into a-Si:H films prepared for a discharge frequency f = 60 MHz is significantly low compared to those for f = 13.56, 40 MHz. These results suggest that the deposition of high quality a-Si:H films at a high rate can be realized by the cluster-suppressed plasma CVD method together with very high frequency discharges.