In one embodiment, a semiconductor device has a substrate, a first semiconductor chip, an electrode, a first and second connection member, and a first and second sealing member. The electrode is disposed on the first semiconductor chip and contains Al. The first connection member electrically connects the electrode and the substrate and contains Au or Cu. The first sealing member seals the first semiconductor chip and the first connection member. One or more second semiconductor chips are stacked on the first sealing member. The second sealing member seals the first connection member, the one or more second semiconductor chips, and the one or more second connection members. A ratio of a total weight W1 of Cl ions and Br ions in the first sealing member to a weight W0 of resins of the substrate and the first sealing member is 7.5 ppm or lower.