Patent ID: 8164231

Claim:
An electret device comprising: a first substrate formed with a plurality of recess portions on a main surface thereof; a second substrate arranged so as to be opposed to said first substrate; and a plurality of electret films so formed on said main surface of said first substrate as to directly cover at least inner surfaces of said recess portions, wherein said first substrate and said second substrate are relatively movable with each other along a direction intersecting with a direction that said first substrate and said second substrate are opposed to each other, one of said first substrate and said second substrate and the other of said first substrate and said second substrate constitute a movable substrate and a fixed substrate in an electrostatic induction generator, respectively, and wherein said plurality of said electrets films are formed at prescribed intervals along a direction that said first substrate and said second substrate relatively move; and a plurality of electrodes are formed on the main surface of said first substrate, between the prescribed intervals of electret films.