An integrated circuit includes a substrate and at least one active region. A transistor produced in the active region separated from the substrate. This transistor includes a source or drain first region and a drain or source second region which are connected by a channel. A gate structure is position on top of said channel and operates to control the channel. The gate structure is formed in a trench whose sidewalls have a shape which converges (narrows) in the width dimension towards the substrate. A capacitor is also formed having a first electrode, a second electrode and a dielectric layer between the electrodes. This capacitor is also formed in a trench. An electrode line is connected to the first electrode of the capacitor. The second electrode of the capacitor is formed in a layer shared in common with at least part of the drain or source second region of the transistor. A bit line is located beneath the gate structure. The integrated circuit may, for example, be a DRAM memory cell.