The Goa'uld sarcophagus is advanced technology that is capable of curing diseases, healing injuries, reviving the dead, and extending life by thousands of years.
The first sarcophagus was created by the Goa'uld Telchak who attempted to harness the life-giving energy of the reanimation device of the Ancients, a device which had been designed to heal but which was far too powerful for use on a human host. In modifying its technology to create the sarcophagus, however, Telchak was unable to eliminate all the negative side effects. Repeated use causes a euphoric narcotic effect, significant psychological changes, and acute physical addiction. The side effects may be partially responsible for the evil characteristics of the Goa'uld, and for this reason the Tok'ra do not use the sarcophagus because they believe that it takes away one's soul.
Although the sarcophagus was designed to boost health and longevity and to heal or revive the dead, it is not powerful enough to animate non-living tissue as the reanimation device can. The limits of the human body also prevent its use indefinitely, and eventually the most ancient of the Goa'uld, such as Yu, can no longer benefit from its healing properties. Daniel used the sarcophagus repeatedly after being injured on P3R-636 and afterward experienced intense withdrawal symptoms. When Teal'c was revived from death in a sarcophagus, he believed that he was once again the First Prime of Apophis. O'Neill was repeatedly tortured to death by Ba'al and revived again in a sarcophagus.
SG-1 has been unable to acquire and retain a sarcophagus for study. The only sarcophagus found on Earth was discovered in a Mayan temple in Palenque, Mexico, where it had functioned as a stasis chamber for the Goa'uld Hathor for at least 2000 years. However, it was destroyed shortly after being removed to the SGC.