| 摘要 |
PURPOSE:To obtain an FET of high performance by superposing partial (111) B surface on the surface of a substrate and an epitaxial layer as the shape in which other crystalline surface exists adjacently, and selectively forming a thin operation layer on the (111) surface. CONSTITUTION:A semi-insulating GaAs substrate 11 in which a main surface 11a exists in (100) plane, is anisotropically etched, selected in approx. 2mum of width and approx. 1mum of depth, and a groove 12 of sectional trapezoid in which the bottom width is approx. 3mum and the side surface exists in (111) plane is formed. When the buffer layer 13 of semi-insulating GaAs is epitaxially formed by thermal decomposition of mixture gas of SiH4 and (CH3)3Gs, the growing speed of the (111) B surface is slow, and the oblique surface 13A of (111) B surface is accordingly presented at the certain time point. When N type impurity gas is fed from this time and epitaxial formation is continued to form an operation layer 14, the parts 14A, 14B are formed in thickness of relationship of tA>>tB by similar growing speed difference. A Pt gate electrode 15 is attached to the part 14B, and ohmic electrodes 16, 17 are attached as source and drain to the parts 14A of both sides. Since the channel length can be sufficiently short and the resistance between the source and the drain is formed to be small, high frequency characteristics can be improved. |
