A thin film capacitor for use in an implantable defibrillator. A first dielectric polymer film layer has a metallized film on one side thereof. A second dielectric polymer film layer has a metallized film on one side thereof. The first and second layers are overlain on each other and wound spirally with the metallized film of one layer adjacent the dielectric polymer of the other layer. The beginnings and ends of the first and second metallized films are offset from the respective beginnings and ends of the first and second polymer film layers. The dielectric layers can be tapered in increasing thickness toward the respective beginnings and ends of the layers. The dielectric layers can themselves comprise at least two layers of differing polymer materials, the preferred materials being polyvinylidene fluoride and polyester for improved energy density and self-healing properties.