A semiconductor device includes a circuit region including a peripheral circuit on a substrate; and a cell region adjacent to the circuit region. The cell region includes a cell array region and a connecting region. The cell region also includes a gate stack that includes an interlayer insulating layer and a gate electrode, alternately stacked on the substrate; a channel in the cell array region that extends through the gate stack; a main support in the connecting region that extends through the gate stack; and a contact electrode in the connecting region connected to the gate electrode through the gate stack. The main support includes a first portion extending along a first direction; and a second portion extending from the first portion in a second direction crossing the first direction. At least a portion of the contact electrode is surrounded by the first and second portions of the main support.