A semiconductor device includes an insulating substrate including a substrate, a metal pattern formed on an upper surface of the substrate, and a metal film formed on a lower surface of the substrate, a semiconductor element fixed on the metal pattern, a case surrounding the metal pattern and having a contact portion maintained in contact with the upper surface of the substrate, and an adhesive with which the case and a portion of the upper surface of the substrate outside a portion maintained in contact with the contact portion are bonded together, wherein a plurality of through holes are formed in a peripheral portion of the case, the through holes extending vertically through the case, and wherein the metal film exists in at least part of a place right below the contact portion.