A normally-off type buried channel MOSFET for VLSI circuits

This paper presents the performance of a buried channel MOSFET (BC-MOSFET) that uses the bulk region as the conducting channel in contrast with the surface channel of the conventional device. Normally-off characteristic has been realized with the p-type silicon gate and the ion-implanted n-channel layer. Fabricated short channel BC-MOSFETs with the gate lengths of 1-3 µ have shown a small shift of threshold voltage with changing the gate length or drain bias. These devices also have high carrier mobility of 750 cm2/v.s and high breakdown voltage compared with those of the conventional device. Minimum delay time of 180 ps was obtained with a 13 stage ring oscillator which was constructed with 1 µ BC-MOSFET.