A method for manufacturing first electrode of a capacitor of a semiconductor device is disclosed. After forming a polycrystalline layer composed of grains with microscopic structure to include an impurity in them, the polycrystalline layer is etched to cut the boundary portions of the grains, thereby allowing the surface of the polycrystalline layer to be rugged. The micro-trenches or micro-pillars are formed by using the oxide layer or an anisotropic etching after exposing the surface of the first rugged polycrystalline layer, and epitaxial grains are formed by epitaxial growth, so that cell capacitance can be further increased. The simple process allows the formation of a reliable semiconductor device having regularity and reproducibility, and capable of increasing and adjusting the cell capacitance easily.