NOVELTY - The device (10) has a silicon substrate (11) that forms the pyramid-shaped corrugated portions in a surface of anisotropic etching. The amorphous type silicon thin films (12-15) are formed on the pyramid-shaped corrugated portions by chemical vapor deposition process. An average length of a diagonal of a pyramid forming the pyramid-shaped corrugated portions is defined by preset formula relating the number of vertices of pyramid of an area and visual field range and is smaller than 5`mm. The stacking of silicon thin film is directly joined to silicon substrate.    USE - Photovoltaic device of solar cell module such as silicon thin-film heterojunction solar cell module used in solar cell system (all claimed).    ADVANTAGE - The amorphous type silicon thin films are formed on the pyramid-shaped corrugated portions by chemical vapor deposition process such that the average length of a diagonal of a pyramid forming the pyramid-shaped corrugated portions is defined by preset formula relating the number of vertices of pyramid of an area and visual field range and is smaller than 5`mm so as to reduce the length of the diagonal of corrugated portion, depth of corrugated portion, and the thickness of collector electrode formed on surface of photovoltaic device. Thus, the efficiency of generating photovoltaic device is increased, and the productive time of silicon substrate is reduced effectively. Since the reduced etching amount is used, the thinner silicon substrate is achieved using less material of silicon substrate. Thus, the amount of material such as silver of collector electrode used is reduced effectively. Since the temperature of formation amorphous type silicon thin film is increased, the amorphous type silicon thin film with reduced defect generation is obtained while suppressing the crystallization by direct joining of the fine corrugation to the silicon substrate. Thus, the generation of local epitaxial film to the portion of groove on the corrugated portion is suppressed.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for manufacturing photovoltaic device.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional drawing of the photovoltaic device.    Photovoltaic device (10)    Silicon substrate (11)    Amorphous type silicon thin films (12-15)    Transparent conducting oxides (16,17)    Comb-shaped collector electrodes (18,19)