A method for manufacturing a solar cell, the method comprising: depositing a tunnel layer formed of a dielectric material and an intrinsic semiconductor layer on a back surface of a semiconductor substrate, the semiconductor substrate being formed of single crystal silicon and containing impurities of a first conductive type; implanting impurities of a second conductive type opposite the first conductive type into a first area of the intrinsic semiconductor layer, the intrinsic semiconductor layer being formed of polycrystalline silicon; forming (S3, S5) a diffusion barrier layer on the first area of the intrinsic semiconductor layer; performing a thermal diffusion operation for thermally diffusing a doping source containing impurities of the first conductive type in a second area of the intrinsic semiconductor layer, in which the diffusion barrier layer is not formed, and at the same time in a front surface of the semiconductor substrate to simultaneously form a front surface field region formed of a single crystal at the front surface of the semiconductor substrate and a back surface field region being formed of polycrystalline silicon and an emitter region being formed of polycrystalline silicon at the intrinsic semiconductor layer; performing an etching operation for simultaneously etching the front surface and the back surface of the semiconductor substrate to partially etch a surface of the front surface field region and a surface of the back surface field region, and at the same time to remove the diffusion barrier layer formed on the emitter region; and forming a first electrode on the emitter region and a second electrode on the back surface field region, wherein if the first conductive type is an n-type, a thickness of the back surface field region is less than a thickness of the emitter region through the etching operation, and if the first conductive type is a p-type, the thickness of the back surface field region is greater than the thickness of the emitter region through the etching operation. depositing a tunnel layer formed of a dielectric material and an intrinsic semiconductor layer on a back surface of a semiconductor substrate, the semiconductor substrate being formed of single crystal silicon and containing impurities of a first conductive type; implanting impurities of a second conductive type opposite the first conductive type into a first area of the intrinsic semiconductor layer, the intrinsic semiconductor layer being formed of polycrystalline silicon; forming (S3, S5) a diffusion barrier layer on the first area of the intrinsic semiconductor layer; performing a thermal diffusion operation for thermally diffusing a doping source containing impurities of the first conductive type in a second area of the intrinsic semiconductor layer, in which the diffusion barrier layer is not formed, and at the same time in a front surface of the semiconductor substrate to simultaneously form a front surface field region formed of a single crystal at the front surface of the semiconductor substrate and a back surface field region being formed of polycrystalline silicon and an emitter region being formed of polycrystalline silicon at the intrinsic semiconductor layer; performing an etching operation for simultaneously etching the front surface and the back surface of the semiconductor substrate to partially etch a surface of the front surface field region and a surface of the back surface field region, and at the same time to remove the diffusion barrier layer formed on the emitter region; and forming a first electrode on the emitter region and a second electrode on the back surface field region, wherein if the first conductive type is an n-type, a thickness of the back surface field region is less than a thickness of the emitter region through the etching operation, and if the first conductive type is a p-type, the thickness of the back surface field region is greater than the thickness of the emitter region through the etching operation.