We have developed a new type of amorphous silicon (a-Si) solar cell, called the integrat-ed type a-Si solar cell (cascade type a-Si solar cell), and a new fabrication method for high conversion efficiency a-Si solar cells, called the consecutive, separated reaction chamber method. With this method, we were able to improve the conversion efficiency of Glass/SnO,/p(SiC)-i-n/Metal to a level of 9.28% with a size of 2 mm x 2 mm, to a level of 7.58% with a size of 10 cm x 10 cm, and to level of 6.14% with a size of 20 cm x 20 cm. We have also proposed a new type of a-Si solar cell, called the "multi-gap amorphous solar cell (stacked cell)" which consists of a-Si:N:H, a-Si:H, and a-Si:Sn:H to improve conversion efficiency. The theoretical limit efficiency of the three band-gap amorphous solar cell is estimated to be 24%. The calculation for the optimization of the integrated type multi-gap solar cell was done. Integrated type a-Si solar cells have been applied both to consumer electronics and power generating systems.