NOVELTY - Solar cell comprises: a p-type semiconductor substrate (10c); a back surface field (BSF) layer (40a) formed with aluminum compound on an opposite surface of a light-receiving surface of the p-type semiconductor substrate; and a back surface electrode (54) formed on the BSF layer to electrically connect to the BSF layer, where the BSF layer has a characteristic of negative fixed charge (NFC).    USE - Used as a solar cell.    ADVANTAGE - The solar cell utilizes the BSF layer that improves the internal reflection efficiency with respect to light transmitted into the solar cell, where the increased internal reflection efficiency of light lengthens the moving path of photons and increases the amount of electron-hole pairs, thus exhibiting high internal quantum efficiency and achieving high optoelectric conversion efficiency.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) fabricating the solar cell comprises: preparing a p-type semiconductor substrate; forming the BSF layer; and forming the back surface electrode on the BSF layer to electrically connect to the BSF layer; and    (2) substrate processing apparatus for fabricating the solar cell, comprising: a processing chamber having a processing space; a substrate support installed in the processing chamber, to support the semiconductor substrates each having a light-receiving surface; a heater to heat the semiconductor substrates arranged on the substrate support; a shower head assembly provided over the substrate support, to inject a process gas into a deposition space through many injecting holes formed in a lower part of the shower head assembly; a gas supply unit to supply the process gas to the shower head assembly; a vacuum pump to make an inner space of the processing chamber vacuous or to discharge a remaining process gas or a reaction by-products outside the processing chamber; and a controller to control the gas supply unit to inject an aluminum source gas, a first purge gas, one or both of an oxidizing agent gas and a nitriding agent gas, and a second purge gas to the processing space, and to control the heater so that a temperature of the semiconductor substrate is within 150-400 degrees C.    DESCRIPTION OF DRAWING(S) - The diagram illustrates a cross-sectional view of the solar cell.    Semiconductor substrate (10c)    Diffusion layer (20b)    Anti-reflection coating (30a)    Back surface field layer (40a)    Back surface electrode (54)