| 摘要 |
PURPOSE:To make it possible to use arsenic in forming a source region, to decrease overlapping capacitance and to obtain a semiconductor device whose high frequency characteristic is improved by thickly forming a gate oxide film, thinly forming a part of the film, implanting arsenic ions, and forming a source regions. CONSTITUTION:An N<->type epitaxial layer 2 is formed on an N<+>-type silicon substrate 1. A P-type well 3 is formed. A gate oxide film having the thickness of 1,400 A and more is grown on the surface. A high-melting-point metal gate electrode 5 is formed thereon. Then, P-type impurities are implanted into the epitaxial layer 2. Thermal diffusion is performed, and a P-type channel layer 6 is formed. Then, a photoresist film 11 is formed in a region other than a source forming region. The gate oxide film 4 undergoes dry etching. The thickness of the film of a part 4a is made to be 150-400Angstrom . When arsenic ions are implanted, the P-type well 3 is implanted into the P-type channel region only through the thin part 4a. This part is heat-treated, and an N<+>-type source region 7 is formed. Then, a protecting oxide film 8 is formed. Holes are provided at the corresponding places of the source region 7 and the P-type well region 3, and source electrodes 9 are formed. As a result, the input capacitance is decreased, and the high frequency characteristic can be improved. |
