The two instruments most commonly used to check the continuity (a complete circuit), or to measure the resistance of a circuit or circuit element, are the OHMMETER and the MEGGER (megohm meter). The ohmmeter is widely used to measure resistance and check the continuity of electrical circuits and devices.
http://www.tpub.com/neets/book3/7l.htm
Here is shown a Do It Yourself kit for making silicon atoms and crystals to demonstrate how semiconductor crystals work and how they are used to make transistor switches.
http://www.virlab.virginia.edu/VL/MOS_kit.htm
Semiconductor glossary, materials, directory, Hall of Fame, and semiconductor Notes.
http://www.semi1source.com/s1s/
One-stop semiconductor information center; contains glossary, hall of fame, useful links as well as information on materials, processes, and devices.
http://www.semi1source.com
http://www.hut.fi/Misc/Electronics/circuits/semiconductor_relays.html
Tutorial on diode fabrication process
http://www.electricalimput.net/