Thin film tensile testers using an electrostatic force grip system were developed to enable increased reliability in MEMS devices. This grip system uses electrostatic force to chuck a thin film specimen. The chucking force is easily controlled and the damage to the specimen during testing can be minimized. With these testers, silicon, silicon-dioxide, and silicon-nitride thin films fabricated with surface micromachining were tensile-tested in a vacuum and in air. The specimens were 2 to 10 μim wide, 30 to 300 μm long, and 0.7 to 2.0 μm thick. We compare the strength of these films and discuss the fracture properties of the films and the effect of the environment.