Who invented the transistor?

The Bipolar Junction Transistor was invented by two scientists, William Sahkely, John Bardeen and Walter Brattain, in 1948. The two of them both worked at Bell Labs, and were trying to find something to replace the bulky and heat wasting vacuum tubes. They had been trying to make a Field Effect Transistor using copper oxide when they discovered a different amplifying effect produced by closely-spaced metal contacts touching Germanium semiconductor. They won the Nobel Prize in Physics for their work in 1956, along with William Shockley, who improved upon their design.
When the Bell Labs scientists continued to investigate a possible FET transistor, they discovered that one of these had already been patented by Physicist J. Edgar Lilienfeld. Lilienfeld's insulated-gate FET (or MOSFET) was based on thin film semiconductor deposited on glass, and was invented over 25 years before the BJT, in the early 1920s (http://www.physlink.com/education/AskExperts/ae414.cfm)