US Patent 7799591 Semiconductor device and method for manufacturing the same

A semiconductor device comprises a first contact plug, a first structure and a second insulating layer, or comprises a first contact plug, a first structure, a protruding region and a second insulating layer. The first contact plug extends in a predetermined direction and including a step converting a cross section area of the first contact plug perpendicular to the predetermined direction discontinuously via the step in one end side. The second insulating layer is formed on side surface of a part of the first contact plug closer to the first structure than the step, or on side surfaces of the protruding region and a part of the first contact plug closer to the first structure than the step.