Grooved gate transistor having source and drain diffused layers with

Abstract

A finely structured grooved gate transistor of which the threshold voltage does not decrease in spite of the small size and of which the threshold voltage of the transistor can be adjusted by shape. The shape of a groove corner of the transistor as a semiconductor device is contained in a concentric circle having a radius of curvature r.+-.L/5 (L: channel length) and the radius of curvature r, i.e., the geometric parameter has a relationship with the doping concentration as shown in FIG. 1B. Alternatively, the average (a+b)/2 (geometric parameter) of the sum of the two sides opposite the right angle of a right triangle formed of a straight line in contact with the gate bottom in parallel to the substrate surface of a grooved gate transistor, a perpendicular line to the substrate bottom surface from the source and drain ends at a portion formed with a channel and a straight line in contact with the groove corner has a relationship with the doping concentration as shown in FIG. 1B. The threshold voltage is not reduced even when the channel length is decreased by adjusting the groove shape and the doping concentration.