In a contact hole of an interlayer insulating film, a tungsten film forming a contact plug is embedded via a barrier metal. The interlayer insulating film is formed by sequentially stacked HTO and BPSG films. The BPSG film has an etching rate faster than that of the HTO film with respect to a hydrofluoric acid solution used in wet etching of preprocessing before formation of the barrier metal. After the contact hole is formed in the interlayer insulating film, a width of an upper portion of the contact hole at the BPSG film is increased in a step-like shape, to be wider than a width of a lower portion at the HTO film by the wet etching before the formation of the barrier metal, whereby an aspect ratio of the contact hole is reduced. Thus, size reductions and enhancement of the reliability may be realized.