Tesla shares were last up 1.4 per cent at $555 after the bell, building on a 7.2 per cent gain during trading when brokerage New Street Research raised its price target to $800.
Tesla's market value also puts Musk a step closer to earning the first $346 million tranche of options in a record-breaking pay package.
The $100 billion valuation needs to stay for both a one-month and six-month average in order to trigger the vesting of the first of 12 tranches of options granted to Musk to buy Tesla stock.
Tesla, which is already valued more than Ford Motor Co and General Motors Co combined, has seen its stock more than double in the last three months, fuelled by a rare quarterly profit in October, news of production ramp-up in its China factory and better-than-expected annual car deliveries.
In another win, Tesla reached a settlement with Michigan to allow it to directly deliver its vehicles to customers in the state, a person familiar with the agreement said on Tuesday.