NOVELTY - A silicon-containing curable composition comprises (in parts mass) silicon-containing polymer (A) (100) obtained by hydrolysis-condensation of organosilane mixture containing organosilanes (I)-(V), prepolymer (B) (0-200) obtained by hydrosilylating ( alpha ) component comprising cyclosiloxane compound (VI), and ( beta ) component containing 1,2,4-trivinyl cyclohexane, vinyl-group containing compound (VII) and/or triazinane-compound (IX), and linear siloxane compound (C) (0.1-30), organic peroxide (0.0001-10 parts mass) and metal catalyst (0-1) (D) and filler (E) (0-1500).    USE - Silicon-containing curable composition is used for cured material (claimed). Uses include but are not limited to semiconductor package, light emitting diode, display material, optical material, recording material, printed circuit board, solar cell, insulating material, fuel cell, building material etc.    ADVANTAGE - The cured material obtained using silicon-containing curable composition has excellent heat resistance, crack resistance, mechanical strength, hardenability, adhesiveness and light resistance.    DETAILED DESCRIPTION - A silicon-containing curable composition comprises (in parts mass) silicon-containing polymer (A) (100) obtained by hydrolysis-condensation of organosilane mixture containing organosilane of formula: R1-SiX3 (I) (5-50 mol%), organosilane of formula: R2-SiX3 (II) (0-50 mol%), organosilane of formula: R3-R4-SiX2 (III) (0-40 mol%), organosilane of formula: R5-SiX3 (IV) (0-50 mol%) and organosilane of formula: R6-SiX3 (V) (0-40 mol%), and has molecular weight of 300-100000, prepolymer (B) (0-200) obtained by hydrosilylating ( alpha ) component comprising cyclosiloxane compound of formula (VI), and ( beta ) component containing 1,2,4-trivinyl cyclohexane, vinyl-group containing compound of formula (VII) and/or triazinane-compound of formula (IX), and having 2 or more silane groups in each molecule, and linear siloxane compound (C) (0.1-30) having 2 or more carbon-carbon double bonds having reactivity with Si-H or Si-CH3 groups in molecule, organic peroxide (0.0001-10 parts mass) and metal catalyst (0-1) (D) and filler (E) (0-1500).    R1=2-6C alkenyl;    R2=H or 1-6C alkyl;    R3,R4=phenyl (optionally substituted by H, 1-6C alkyl, 2-6C alkenyl) or 1-6C alkyl;    R5=phenyl (optionally substituted by 1-6C alkyl);    R6=2-10C epoxy;    X=hydroxy, 1-6C alkoxy or halo;    R7-R9=phenyl (optionally substituted by 1-6C alkyl) or 1-6C alkyl;    f=2-10;    g=0-8;    f+g=2 or more;    R10=2-10C alkenyl;    R11,R12=1-10C alkyl, 2-10C alkenyl or 2-10C epoxy;and    n=1 or 2.    At least 1 of R2, R3 and R4 is methyl. An INDEPENDENT CLAIM is included for cured material, which is obtained by hardening silicon-containing curable composition.