Heterojunction tunnel field effect transistors (hTFETs) incorporating one or more oxide semiconductor and a band offset between at least one of a channel material, a source material of a first conductivity type, and drain of a second conductivity type, complementary to the first. In some embodiments, at least one of p-type material, channel material and n-type material comprises an oxide semiconductor. In some embodiments, two or more of p-type material, channel material, and n-type material comprises an oxide semiconductor. In some n-type hTFET embodiments, all of p-type, channel, and n-type materials are oxide semiconductors with a type-II or type-III band offset between the p-type and channel material.