Samsung Electronics has named a new executive to head its bread-and-butter memory division, after posting its worst net profit in four years last week.

"Mr. Cho Soo-in is the executive vice president of the memory division," a Samsung spokesman said.

Hwang Chang-gyu, who had been both president of the semiconductor business and head of the memory chip division, retains his semiconductor title, Samsung said.

Executive changes in the middle of the year are extremely rare at top South Korean companies.

Margins at Samsung's semiconductor division fell to 8 percent in the April-June quarter, from 12 percent in the first quarter and 22 percent in the year-earlier period, as overproduction led to price declines estimated at more than 40 percent in the second quarter alone.