A semiconductor device is configured that two or more semiconductor elements are stacked and mount on a lead frame, the aforementioned lead frame is electrically joined to the semiconductor element with a wire, and the semiconductor element, the wire and an electric junction are encapsulated with a cured product of an epoxy resin composition for encapsulating semiconductor device, and that the epoxy resin composition for encapsulating semiconductor device contains (A) an epoxy resin; (B) a curing agent; and (C) an inorganic filler, and that the (C) inorganic filler contains particles having particle diameter of equal to or smaller than two-thirds of a thinnest filled thickness at a rate of equal to or higher than 99.9% by mass.