Alexei Semin was bornon 10 April 1981 in Russia. Alexei Semin in 1990 graduated from Kazan State University (Department of Scientific Communism). From 1991 he worked in investment company Obrazovanie, which made several privatizing deals on Tatarstan market. From 1995 to 2000 Semin was State Council deputy of Tatarstan Republic, from 1999 to 2005 he headed the republic's Committee on bankruptcy cases and financial sanitation. Kazan mass media guessed that some lots from financial sanitation were bought by Semin's companies. Today Semin owns 320,000 sq. m of real estate, 3,000 hectares of land in Kazan, 22,000 hectares in its suburbs. His companies reconstruct and renovate old buildings in the center of Kazan. In Moscow, close to Rublevskoe highway, Semin built a village of rented houses.
Semenov was invited to training camp with the New York Rangers for the 2009–10 season and was offered a one-year contract before the season to serve as the team's seventh defenseman
On July 27, 2007, Semenov signed a one-year contract with the San Jose Sharks
Upset at his assignment to the Rochester Americans at the start of the 2006–07 season, Semenov left Rochester after four games to play for Salavat Yulaev Ufa in Russia
After playing three full seasons for the Oilers and their top farm club, the Hamilton Bulldogs, he was traded to the Florida Panthers for a conditional draft pick in the 2006 NHL Entry Draft on November 19, 2005
In 2001, Semenov was awarded the Max Kaminsky Trophy as the best defenceman in the Ontario Hockey League (OHL)
Semenov was selected by the Edmonton Oilers in the second round of the 1999 NHL Entry Draft, 36th overall
Alexei Anatolevich Semenov (Russian: Алексей Семёнов, Alexey Semyonov; born April 10, 1981) is a Russia professional ice hockey defenceman