A semiconductor integrated circuit device has a semiconductor memory cell array including word lines, data lines and a plurality of memory cells provided at cross points of the word and data lines. Each memory cell has a cell selection transistor and an information storage capacitor connected in series. The cell selection transistor in one cell includes first and second doped regions formed in a main surface of a semiconductor substrate, a first insulating film formed on the main surface between the first and second doped regions and a control electrode layer formed on the first insulating film between the first and second doped regions. The first doped region is connected with a data line, while the control electrode is connected with a word line. The information storage capacitor includes a second insulating film formed on the wall of one trench formed on the main surface of the substrate, an electrode layer formed on the second insulating film and serving as a first electrode of the capacitor, a dielectric film formed on the electrode layer and a conducting material provided to fill a space defined by the dielectric film in the trench and serving as a second electrode of the capacitor. The second doped region of the transistor terminates at the wall of the trench. A conducting layer is provided to extend both on the second doped region and the conducting material in the cell to electrically interconnect them for the series connection.