Tokyo stocks tumbled Monday morning, with selling of technology and exporter-related issues spurred by plunges in U.S. semiconductor-related shares late last week and a stronger yen against the U.S. dollar. The 225-issue Nikkei Stock Average fell 984.84 points, or 2.48 percent, from Friday to 38,704.10. The broader Topix index was down 61.43 points, or 2.25 percent, at 2,665.37. The dollar briefly weakened to the mid-146 yen range on yen buying amid speculation that the Bank of Japan could move to end its negative interest rate policy in March. At noon, the dollar fetched 147.06-09 yen compare…