Integrated passive devices for silicon on insulator (SOI) FinFET technologies and methods of manufacture are disclosed. The method includes forming a passive device on a substrate on insulator material. The method further includes removing a portion of the insulator material to expose an underside surface of the substrate on insulator material. The method further includes forming material on the underside surface of the substrate on insulator material, thereby locally thickening the substrate on insulator material under the passive device.