NOVELTY - The method comprises forming (S11) a P-type layer, forming (S12) an I-type layer including sub-layers successively stacked on the P-type layer using gas mixtures, and forming (S13) an N-type layer on the I-type layer. The gas mixtures include fluoride and hydride having different gas ratios, respectively. The step of forming the an I-type layer includes forming a first I-type sub-layer on the P-type layer using the gas mixture at a first gas ratio, and forming a second I-type sub-layer on the first I-type sub-layer using the gas mixture at a second gas ratio.    USE - The method is useful for manufacturing a P-I-N microcrystalline silicon structure for thin-film solar cells (claimed).    ADVANTAGE - The method is capable of effectively preventing interfacial damages between the I-type layer and the P-type layer due to excessive fluoride and reducing the internal defects within the I-type layer thus increasing the yield of the solar cells.    DETAILED DESCRIPTION - The method comprises forming (S11) a P-type layer, forming (S12) an I-type layer including sub-layers successively stacked on the P-type layer using gas mixtures, and forming (S13) an N-type layer on the I-type layer. The gas mixtures include fluoride and hydride having different gas ratios, respectively. The step of forming the an I-type layer includes forming a first I-type sub-layer on the P-type layer using the gas mixture at a first gas ratio, forming a second I-type sub-layer on the first I-type sub-layer using the gas mixture at a second gas ratio, and forming a third I-type sub-layer on the second I-type sub-layer using the gas mixture at a third gas ratio. The first gas ratio is 8%. The second gas ratio is 15-35%. The third gas ratio is 35-50%. The first I-type sub-layer has a crystallinity of 45-80%. The steps of forming the P-type layer, the I-type layer and the N-type layer are performed by a plasma-enhanced chemical vapor deposition technique. An INDEPENDENT CLAIM is included for a P-I-N microcrystalline silicon structure of thin-film solar cells.    DESCRIPTION OF DRAWING(S) - The diagram shows a flow chart of a method for manufacturing a P-I-N microcrystalline silicon structure of thin-film solar cells.    Forming a P-type layer (S11)    Forming an I-type layer including sub-layers successively stacked on the P-type layer using gas mixtures (S12)    Forming an N-type layer on the I-type layer. (S13)