Yamaha Corporation

Toshio Fujioka

Shigeru Suga

Katsuyuki Yokoi

On an insulating film (12) covering the surface of a semiconductor substrate (10), a gate electrode layer (14), a gate insulating film (16), and a semiconductor layer (18) such as silicon are sequentially deposited to form an under-gated MOS transistor. A flat coating film such as resist is formed covering the semiconductor layer (18). The coating film is then etched back to expose the surface of the semiconductor layer (18) at the area above the gate electrode layer (14). The left coating film is used as the mask for the selective growth of a mask material layer (24) such as tungsten on the exposed surface of the semiconductor layer (18) with a side-projection. After removing the left coating film, impurity ions such as BF2 are selectively injected in the semiconductor layer (18) using the mask material layer (24) as the mask to form a source region (18S) and a drain region (18D).

Method of making staggered gate MOSTFT

For enhancement of device stability, there is disclosed a semiconductor device fabricated on a semiconductor substrate comprising (a) source and drain regions formed in a surface portion of the semiconductor substrate and spaced from each other by a channel region, (b) a gate insulating film formed on the channel region, (c) a gate electrode structure formed on the gate insulating film, and (d) a passivation film of an insulating material covering the gate electrode structure and containing hydrogen-bonded-silicons equal in number to or less than 5.times.10.sup.21 per cm.sup.3, and the unstable hydrogen-bonded-silicons are decreased in number so that the semiconductor device only have a decreased trap density which results in stable operation.

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Hamamatsu, Japan

Toshio Fujioka