To obtain semiconductor device with a good adhesion between a lead frame and a sealing-use hardened resin material and with an excellent soldering heat resistance, by sealing a semiconductor element on the lead frame with a compsn. comprising an epoxy resin, a phenolic resin with a specific melt viscosity value or less, an inorg. filler and an adhesion providing agent.

A phenolic resin having a melt viscosity of 5 pise or less at 150°C is applied. As an adhesion providing agent is used at least one member selected from the group consisting of an org. titanium compd., a rosin type resin and an indene type resin. The ratio: (the epoxy group of the epoxy resin)/(the phenolic hydroxide group of the phenolic resin) (equivalent ratio) is pref. 0.5-2.0. As an inorg. filler used are inorg. powders such as a molten silica, a crystalline silica and alumina. The compsn. pref. comprises 70-95 wt.% of the inorg. filler. The adhesion providing agent is used usually at the concn. of 0.1-5.0 wt.% based on the total compsn. Further, a hardening accelerating agent, a mold release agent, a flame retarding aid, a colorant, or the like are added as required.