A photovoltaic device has a transparent substrate, a transparent electrode layer, a photovoltaic layer, and a back electrode which are stacked in this order. The photovoltaic layer has a p-type a-SiC layer provided on the transparent electrode layer, a buffer layer provided on the p-type a-SiC layer, a photosensitive layer provided on the buffer layer, and an n-type semiconductor layer provided on the photosensitive layer. The buffer layer is an a-SiC layer first deposited on the p-type a-SiC layer and then subjected to a plasma treatment. The plasma treatment should be carried out using a gas selected from a group consisting of hydrogen (H.sub.2), Argon (Ar), Helium (He), Neon (Ne), Krypton (Kr), and Xenon (Xe). In the device, the buffer layer may be composed of a microcrystalline SiC layer or an amorphous SiC layer. The buffer layer may have a thickness ranging from about 10 .ANG. to about 100 .ANG., and may be formed by a plasma-CVD process.