Abstract: A continuous deposition process and apparatus for depositing semiconductor layers containing cadmium, tellurium or sulfur as a principal constituent on transparent substrates to form photovoltaic devices as the substrates are continuously conveyed through the deposition apparatus is described. The film deposition process for a photovoltaic device having an n-type window layer and three p-type absorber layers in contiguous contact is carried out by a modular continuous deposition apparatus which has a plurality of processing stations connected in series for depositing successive layers of semiconductor films onto continuously conveying substrates. The fabrication starts by providing an optically transparent substrate coated with a transparent conductive oxide layer, onto which an n-type window layer formed of CdS or CdZnS is sputter deposited. After the window layer is deposited, a first absorber layer is deposited thereon by sputter deposition.