Electronic material filler, high-frequency substrate, and electronic material slurry

An electronic material filler that is a silica particle material,

• wherein the silica particle material has a particle diameter of 100 nm to 2000 nm and a specific surface area of 2 m2/g to 35 m2/g,
• when heated at 200° C., the silica particle material generates 40 ppm or less of water per 1 m2 of surface area, and
• the silica particle material has a functional group represented by formula (A):
• —OSiX′X2X3 and a functional group represented by formula (B):
• —OSiY′Y2Y3 on a surface thereof, and does not have an OH group on the surface thereof, wherein in the formulas (A) and (B):
• X1 represents a vinyl group, a phenyl group, a phenylamino group, an alkyl group having four or more carbon atoms, a methacryl group, or an epoxy group;
• X2 and X3 are each independently selected from —OSiR3 and —OSiRY4Y5Y6;
• Y1 represents R;
• Y2 and Y3 are each independently selected from R and —OSiY4Y5Y6;
• Y4 represents R;
• Y5 and Y6 are each independently selected from R— and —OSiR3;
• Rs are each independently selected from alkyl groups having one to three carbon atoms;
• and
• any of X2, X3, Y2, Y3, Y5, ad Y6 is optionally bonded to an adjacent functional group which is any of X2, X3, Y2, Y3, Y5, and Y6 via —O—.