The characteristics of a semiconductor device including a trench-gate power MISFET are improved. The semiconductor device includes a substrate having an active region where the power MISFET is provided and an outer circumferential region which is located circumferentially outside the active region and where a breakdown resistant structure is provided, a pattern formed of a conductive film provided over the substrate in the outer circumferential region with an insulating film interposed therebetween, another pattern isolated from the pattern, and a gate electrode terminal electrically coupled to the gate electrodes of the power MISFET and provided in a layer over the conductive film. The conductive film of the pattern is electrically coupled to the gate electrode terminal, while the conductive film of another pattern is electrically decoupled from the gate electrode terminal.