Complementary N- and P-channel Schottky Junction Transistors

Micropower circuits based on sub-threshold (i.e. weakly inverted) MOSFETs use complementary n- and p-channel transistors in the same CMOS ciruits. Complementary behavior means that if equal and opposite voltages are applied to the p-channel device compared to those on the n-channel device than equal and opposite currents will flow. To achive complementary behaviorin a conventional CMOS circuit the width of the p-channel device has to be 2-3 times larger than that of the n-channel device. This is due to the lower mobility of holes compared to electrons. As a result the p-channel device teks up more space on the chip than the n-channel device. As well as consuming costly silicon 'real estate' the p-channel device is slower becasue of its larger input capacitance.This disclosure explains how micropower circuits can be fabricated using the Schottky Junction Transistor approach taught in 99-038. In particular the circuits can use complementary n- and p-channel SJTs that have substantially equal gate length and gate width. Thgis provides a substantial saving in the total area of an integrated circuit. It alos allows a complementary SJT circuit to operate faster than a similar design using conventional CMOS, because of the reduced capacitance of the p-channel SJTs.