The method for mfg. polysilicon/polysilicon capacitance is applicable to the substrate with the insulation zone and the initiative zone. The first insulation zone is formed on the surface of the substrate. Then, the first conductor layer, the second insulation zone and the second conductor layer are formed on the first conductor layer in sequence. Etching the second conductor layer and the secondinsulation zone forms the upper electrode plate of the capacitance and the dielectric layer on the first conductor layer. Etching the first conductor layer and the first insulation zone forms the lower electrode plate of the capacitance on the insulation zone and the grid electrode structure on the initiative zone.