JPS5646557A - Transistor - Google Patents

Abstract

PURPOSE:To obtain an FET which incorporates a small size and stable characteristics by forming insulating layers selectively on the recessed surface of a P type substrate and filling N type layers therein. CONSTITUTION:Field oxide films 22 are formed on the (100) surface of a P type Si substrate 21, SiO2 film 23, Si3N4 film 24 and a polysilicon gate electrode 25 are formed thereon, the an SiO2 film 26 is covered thereon. The substrate 21 is anisotropically etched, and grooves 27, 28 are opened therebetween. At this time the grooves are partly intruded as designated by 29, 30 underneath the film 23. An O2 ions are implanted, and SiO2 layers 31, 32 are formed on the surfaces of the grooves. At this time the crystallinity of the P type thin layer on the layers 31, 32 is not damaged. When an N<+> type epitaxial layer 33 covers the P type thin layer, it is erased. Then, the layer 33 is etched, N<+> type layers 41, 42 are formed thereon, SiO2 films 43, 44 are covered thereon, are opened with windows 45-47, and aluminum electrodes 48-50 are attached thereto. The depths of the source and the drain are determined by the depths of the grooves in the vicinity of the upper ends 29, 30, and can be accurately determined by anisotropic etching process. Aluminum punch through phenomenon is prevented by the layers 31, 32, and is thus hardly taken place. In this manner there can be obtained an FET which incorporates small size and preferable characteristics.