Google is your friend....Google knows all...(more or less, a little fuzzy around the edges sometimes, but mostly in the ballpark..)
Semiconductor transistors? No, not in 1939. 1946, 1947 depending on what you want to call invented? - actual semiconductor effect? patented? demonstrated? Dec 23, 1947 is the most cited date. IIRC there was about 6-10 months from the time the actual device worked in the lab till when it was announced to the world (Dec 1947) Actually the field effect transistor was discovered in 1925. A vacuum tube (valve) diode was invented in 1904, semiconductor version was developed in the early 40's.
Silicon crystals that exhibited the 'diode effect' were used in the 1920,1930 as detectors in the crystal radios.