To achieve high integration of a PRAM.

A semiconductor device comprises: a sidewall insulating film covering an inner wall surface of a hole of a first interlayer insulating film; a contact plug embedded in the hole via the sidewall insulating film; a lower electrode arranged so as to be connected with the contact plug in a predetermined region on the first interlayer insulating film; a second interlayer insulating film covering the first interlayer insulating film including the lower electrode; an opening penetrating through the second interlayer insulating film, exposing a part of a side end surface of the lower electrode, and formed to a predetermined depth of the first interlayer insulating film; a phase change material layer arranged in a predetermined region on the second interlayer insulating film including the opening, and connected to the part of the side end surface of the lower electrode at the opening; and an upper electrode arranged on the phase change material layer.