FIELD-EFFECT transistors (FETs), though simpler to make than BJTs, were held back for many years by manufacturing difficulties with the gate insulation layer. In the 1970s the problems were solved and FET technology developed at a rapid pace. FETs are now more widely used than BJTs and have made an enormous impact on integrated circuit (IC) technology. Not only have very low-power CMOS (complementary metal oxide-semiconductor, a type of FET) ICs have become reliable and cheap, but also power devices such as HEXFETs and VMOS FETs have replaced many types of power bipolar devices, and semiconductor memories are no more than huge arrays of MOSFETs.
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