CREATE TABLE table_9729 ("Tournament" TEXT, "Surface" TEXT, "Week" TEXT, "Winner" TEXT, "Finalist" TEXT, "Semi finalists" TEXT)

Which Surface has a Semi finalists of conchita mart nez arantxa s nchez?
SELECT "Surface" FROM table_9729 WHERE "Semi finalists" = 'conchita martínez arantxa sánchez'
SELECT "Surface" FROM "table_9729" WHERE "Semi finalists" = 'conchita martínez arantxa sánchez'