A semiconductor integrated circuit device having a reservoir capacitor and a method of manufacturing the same are provided. A first insulating layer is formed on a semiconductor substrate including a first region and a second region. A first conductive layer is formed on the first insulating layer, and a second insulating layer is formed on the first conductive layer. The second insulating layer is patterned to be left in a portion of the first region. A second conductive layer is formed on the second insulating layer and the first conductive layer. The second conductive layer is etched to expose a partial surface of the first conductive layer in the first region. The second conductive layer and the first conductive layer are etched to form a reservoir capacitor in the first region and form a gate in the second region.