A semiconductor device comprising: a first thick plate portion; a first semiconductor element on said first thick plate portion and comprising a first spacer; wherein the first thick plate portion is electrically connected to an electrode on a lower surface side of the first semiconductor element, and that is formed by a conductor; a second thick plate portion laterally adjacent to the first thick plate portion; a second semiconductor element on said second thick plate portion and comprising a second spacer; wherein said second thick plate portion is electrically connected to an electrode on a lower surface side of the second semiconductor element, and that is formed by a conductor; a third thick plate portion that is electrically connected to an electrode on an upper surface side of the first semiconductor element via said first spacer, and that is formed by a conductor; a fourth thick plate portion that is electrically connected to an electrode on an upper surface side of the second semiconductor element via said second spacer, and that is formed by a conductor; a first thin plate portion integral with the second thick plate portion and extending towards the first thick plate portion, formed by a conductor, and thinner than both the first thick plate portion and the second thick plate portion; and a second thin plate portion integral with the third thick plate portion and extending towards the fourth thick plate portion, formed by a conductor, and thinner than both the third thick plate portion and the fourth thick plate portion, wherein the first thin plate portion and the second thin plate portion are fixed together and electrically connected in a lateral position between the position of the first thick plate portion and the second thick plate portion and in a position midway between the position of the first thick plate portion and the position of the third thick plate portion in the thickness direction of the first semiconductor element. a first thick plate portion; a first semiconductor element on said first thick plate portion and comprising a first spacer; wherein the first thick plate portion is electrically connected to an electrode on a lower surface side of the first semiconductor element, and that is formed by a conductor; a second thick plate portion laterally adjacent to the first thick plate portion; a second semiconductor element on said second thick plate portion and comprising a second spacer; wherein said second thick plate portion is electrically connected to an electrode on a lower surface side of the second semiconductor element, and that is formed by a conductor; a third thick plate portion that is electrically connected to an electrode on an upper surface side of the first semiconductor element via said first spacer, and that is formed by a conductor; a fourth thick plate portion that is electrically connected to an electrode on an upper surface side of the second semiconductor element via said second spacer, and that is formed by a conductor; a first thin plate portion integral with the second thick plate portion and extending towards the first thick plate portion, formed by a conductor, and thinner than both the first thick plate portion and the second thick plate portion; and a second thin plate portion integral with the third thick plate portion and extending towards the fourth thick plate portion, formed by a conductor, and thinner than both the third thick plate portion and the fourth thick plate portion, wherein the first thin plate portion and the second thin plate portion are fixed together and electrically connected in a lateral position between the position of the first thick plate portion and the second thick plate portion and in a position midway between the position of the first thick plate portion and the position of the third thick plate portion in the thickness direction of the first semiconductor element.