| 摘要 |
PURPOSE:To control the width of a recess independently and with good reproducibility by a method wherein a two-layer structure, which is composed of a first thin dielectric film whose etching rate is fast and a second thick dielectric spacer layer whose etching rate is slow, is formed. CONSTITUTION:After a source electrode and a drain electrode 3, 4 have been formed on an active layer 2 on a semiconductor layer 1, a first thin dielectric film 5a whose wet etching rate is fast is formed, and, furthermore, a second dielectric spacer layer 5b whose etching rate is comparatively fast is formed. The first thin dielectric film 5a and the second thick dielectric spacer layer 5b are etched by RIE by making use of a resist pattern as a mask; these layers are removed in such a way that the size can become the same as that of the resist pattern. After that, a desired amount of the first thin dielectric film 5a is side-etched by a wet etching method on the basis of the side etching rate of the first dielectric film 5a; after that, a recess 7 is formed at the active layer 2; after that, a gate metal is evaporated; a gate electrode 8 is formed inside the recess 7 by a lift-off method. By this setup, the lift-off performance is enhanced; the width of the recess and the depth of the recess can be controlled with good reproducibility and independently of each other.
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