JPS5688364A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a punch through transistor having high responding speed in high yield while simplifying the film formation by continuously increasing the thickness of the gate insulating film forming an IGFET from the vicinity of source region to the vicinity of drain region. CONSTITUTION:Drain and source regions 9 and 10 having different conductivity type from a semiconductor substrate 8 are diffused at an intefval less than 3m in the substrate 8, and a gate insulating film (c) is covered on a channel region disposed therebetween over the edges of the regions 9 and 10, thereby forming an IGFET. In this configuration the thickness of the film (c) is gradually increased continuously from the vicinity of the region 10 to the vicinity of the region 9. This can be formed by first covering a uniformly thick insulating film 11 on the entire surface contining the regions 10 and 9, etching them in tapered shape. Thereafter, a gate electrode 12 is covered on the film (c), a window is opened at the film 11, and the drain and source electrodes 13 and 14 are respectively mounted on the regions 9 and 10.