Organic insulating material, varnish for resin film using the same, resin film and semiconductor device

An organic insulating material consisting essentially of a prepolymer of a cage structure compound having a polymerizable unsaturated bond-containing group and a cage structure with an adamantane structure as the minimal unit, wherein the prepolymer has a number-average molecular weight of between 2,000 and 500,000 based on polystyrene and measured by gel permeation chromatography, wherein the prepolymer comprises unsaturated bonds produced by reaction between the polymerizable unsaturated bonds, and the unreacted polymerizable unsaturated bonds, wherein the prepolymer has a residue rate of unreacted polymerizable unsaturated bonds of between 20% and 80%, and wherein the cage structure compound is a compound represented by the following formula (2):

• wherein X1 and Y1 each represent one or more groups containing polymerizable unsaturated bonds, and they may be the same or different from each other, R1-R4 each independently represent hydrogen or an organic group, and they may be the same or different from each other, and the symbol n1 represents an integer of 1 or greater.