In a method of forming an ohmic layer of a DRAM device, the metal silicide layer between the storage node contact plug and the lower electrode of a capacitor is formed as the ohmic layer by a first heat treatment under a first temperature and an instantaneous second heat treatment under a second temperature higher than the first temperature. A plurality of cycle number ranges are set up. In another embodiment, a first multi-layer coating deposited on a mirror substrate reflects a first incident radiation within a first band around a first wavelength and a second incident radiation, in an optical path, within a second band around a second wavelength. The male connectors are formed by elastically deformable blades which penetrate into two metallized holes of the board which define the two female connectors. The particle size of the titania composite is small, and the particle size distribution range of the titania composite is controllable.