Curable organopolysiloxane composition and semiconductor device

A curable organopolysiloxane composition comprising:

• (A) an organopolysiloxane of the following average structural formula:
• R1aSiO(4-a)/2
• (wherein R1 designates unsubstituted or halogen-substituted monovalent hydrocarbon groups;
• however, in one molecule at least two groups designated by R1 are alkenyl groups and at least 30 mole % of all groups designated by R1 are aryl groups;
• and “a” is a number ranging from 0.6 to 2.1);
• (B) an organopolysiloxane that contains in one molecule at least two silicon-bonded hydrogen atoms and at least 15 mole % of all silicon-bonded organic groups in the form of aryl groups;
• (C) a branched-chain organopolysiloxane of the following average unit formula:
• (R2SiO3/2)b(R22SiO2/2)c(R23SiO1/2)d(SiO4/2)e(XO1/2)f
• {wherein each R2 independently designates an alkyl group, alkenyl group, aryl group, or an epoxy-containing organic group;
• however, in one molecule at least 5 mole % of all groups designated by R2 are alkenyl groups, at least 15 mole % of all groups designated by R2 are aryl groups, and at least 10 mole % of all groups designated by R2 are epoxy-containing organic groups;
• X designates a hydrogen atom or an alkyl group;
• and “b” is a positive number, “c” is 0 or a positive number,“d” is 0 or a positive number, “e” is 0 or a positive number, “f” is 0 or a positive number, “c/b” is a number ranging from 0 to 10, “d/b” is a number ranging from 0 to 5, “e/(b+c+d+e)” is a number ranging from 0 to 0.3, and
• “f/(b+c+d+e)” is a number ranging from 0 to 0.02};
• and
• (D) a hydrosilylation catalyst;
• wherein component (B) is used in such an amount that the mole ratio of the silicon-bonded hydrogen atoms contained in component (B) to the alkenyl groups contained in components (A) and (C) is in the range of 0.1 to 5;
• component (C) is contained in an amount of 0.1 to 20 parts by mass per 100 parts by mass of the sum of components (A) and (B);
• and
• component (D) is contained in an amount sufficient to accelerate curing of the composition.