The 20-year-old American private, identified only by the initial L, was indicted on charges of breaking into the couple's home in Dongducheon, 70 kilometers north of Seoul, in February and trying to rape the 64-year-old woman.
He is also accused of attacking the couple with a blunt weapon and robbing the woman of her mobile phone after his unsuccessful rape attempt.
"The defendant's crime of breaking into a home and committing assault, robbery and attempted rape against the victims is considered very serious," said the Uijeongbu District Court.
"The punishment cannot be lighter or heavier due to the fact that (the defendant) is a foreigner." "The seriousness of the offense was measured based on the recognition that the defendant is guilty of all of his crimes, on the victims'' testimonies and extent of damage, and on the fact that there has been no agreement (between the sides)," it added.
As a warning against such incidents happening again, South Korean police broke convention by detaining and investigating the American soldier after arresting him at the crime scene. In previous cases, American service members have been handed over to the US military police.
Dongducheon is home to thousands of American soldiers in the 2nd Infantry Division at camps Casey and Hovey. About 28,500 US troops are stationed in South Korea to deter potential aggression from communist North Korea.
The two Koreas are still technically in a state of war since the 1950-53 Korean War ended with a cease-fire, not a peace treaty.