Semiconductor sealant of epoxy resin and organic polymer-grafted silicone polymer

A semiconductor device comprising a semiconductor element sealed with an epoxy resin molding material, the epoxy resin molding material comprising (A) an epoxy resin having at least two epoxy groups per molecule;

• (B) a compound having at least two phenolic hydroxyl groups per molecule;
• and (C) a powder which (1) has a structure comprising a core of solid silicone polymer and a shell of organic polymer, in a weight ratio of solid silicone polymer organic polymer of from 1:1 to 5:1, (2) the solid silicone polymer comprising 80-99.5 mol % of a (RR'SiO.sub.2/2) unit and 0.5 to 20 mol % of at least one of a (RSiO.sub.3/2) unit and a (SiO.sub.4/2) unit as a crosslinking agent, wherein R is an alkyl group of 6 or less carbon atoms, an aryl group or a functional group having a terminal carbon-carbon double-bond, and R' is an alkyl group of 6 or less carbon atoms or an aryl group, and wherein the solid silicone polymer contains 1-10 mol % of siloxane units with carbon-carbon double bond based on the total units of the solid silicone polymer.