A semiconductor device includes: a semiconductor chip; a case having a frame portion that has an inner wall portion surrounding an housing area in which the semiconductor chip is disposed; a buffer member provided on at last part of the inner wall portion of the case on a side of the housing area; a low expansion member provided on said at least part of the inner wall portion with the buffer member interposed therebetween on the side of the housing area; and a sealing member that seals the housing area, wherein the buffer member has a smaller elastic modulus than the case and the sealing member, and wherein the low expansion member has a smaller linear expansion coefficient than the case and the sealing member.