It is an object to provide technology allowing for improvement in productivity of a semiconductor device. A semiconductor device includes: a base plate; an insulating substrate including a ceramic plate integrally bonded to an upper surface of the base plate with no solder layer therebetween and a circuit pattern disposed on an upper surface of the ceramic plate; a semiconductor element mounted on an upper surface of the circuit pattern; a case surrounding the insulating substrate and the semiconductor element over the base plate; an adhesive to adhere a lower portion of the case to an outer peripheral portion of the ceramic plate; and a sealant to seal the interior of the case, wherein the adhesive is in contact with an outer peripheral end of the ceramic plate to an outer peripheral end of the circuit pattern.