The method of forming a lower electrode of a capacitor includes forming an first insulation film over a substrate, and forming a trench in the first insulation film to expose an electrical contact structure. After interaction with an index grating, fringes are formed in a Talbot plane and analyzed by an analyzer grating. The rear contact-point portion includes a contact edge that is thinner than the sliding edge, has a sliding width that is less than that of the sliding edge, and is conductively connected with the plug terminal by passing a sliding path of the sliding edge.