Based on the standard CMOS process,two types of solar cells are desig ned.They are a PN junction photodiode (PD) consisting of an N-well and a p+ source/drain (S/D) region and a PD consisting of a p-sub and n+ S/D region.By analyzing the critical factors affecting the device performanc e,the solar cells with four different geometries are designed and fabricated using standard CMOS process.Th e experimental results demonstrate that the solar cell with an area of 50μm×50μm has the optimal p erformance.The maximum output power obtained at the standard test conditions is 29.44μW/mm²,and the short -circuit current and open-circuit voltage are 76.61μA/mm^2and 0.49V,respectively.A conversion efficiency of 2.94% for p+/N-well solar cell is achieved.Based on the optimal structure parameters,a tandem solar cell connect ed by electrical short-circuit with a p+/N-well PD and an n+/p-sub PD is implemented in CSMC 0.18μm CMOS pr ocess.The solar cell generates a high-voltage output of 0.95V,and the short-circuit current and maximum output power of the solar cell are 13μA/mm^2and 10.5μW/mm²,respectively.The tandem solar cell formed in this paper has the potential for direct applications in wireless autonomous mic rosystems.